Churn and choice are what keeps me on the fence with Elixir too. Over the last few years I went from very excited and built a few things with it to "maybe try again later".
It's just not fun to be in a constant state of package fatigue, especially when a lot of semi-popular libraries are maintained by 1 person. If that 1 person leaves that entire bit of functionality becomes a liability to your application because it's unrealistically demanding to be a solo developer or small team and be responsible to maintain a bunch of libraries that become unmaintained but then also build your application.
This is IMO especially true with a language as powerful as Elixir with macros. Picking up and reading someone else's code can either feel natural or be really hard, to the point where looking at it doesn't feel like the language you know. This makes it doubly hard to read 3rd party library code because you're learning the other person's code and have to mentally deconstruct a lot of advanced patterns if they use them. I don't consider myself that good of a programmer but there's a lot of times where in Elixir, phrases like "this is impossible for me to understand" come up when I've written hundreds of thousands of lines of code in Python but never thought this. I sometimes had the "what am I looking at?" feeling with Ruby too btw.
As for library availability, this is a problem that doesn't come up as often with more main stream web frameworks, at least not in the Python and Ruby eco-system. Sure things go in and out of fashion but both languages have frameworks that include more batteries included or the community has gotten so big that there's a bunch of independently developed libraries that most of the community got behind and supports it so well that it becomes a no-brainer to use it.
So that's what keeps me on the fence and I think some of these problems can be solved with time, but time is a scary thing because waiting a few years feels like an eternity and the outcome after waiting a few years might be waiting a few more years. At some point you need to build whatever you're building and run with it without looking back.
But I think this really comes down to personal preference. I used to think I wanted unlimited choice and an endless world of possibilities. I don't. I want to build web applications quickly using the most straight forward code I can think of and get as many batteries as included as possible while leaning on / contributing back to a massive eco-system. I don't want to be on the front lines of building a new eco-system. I still do think in the very long term (5+ years maybe) Elixir could be a good match for me once there's a lot of libraries that have hit critical mass.
There's plenty of people using it successfully now, and I'm happy there are people who like being closer to early adopters and setting up the initial ground work for an eco-system.
As someone who just started learning Elixir, this comment makes me anxious. I don't think I am going to write some exotic web application or some unique functionality, but at the same time I also don't want to be constantly fighting with the limitations of the stack I choose.
Elixir is an involving platform and community. Think about the Ruby community from years ago, a lot of things are missing, but there is a lot of potentials as well. From my side, I started to see Elixir seriously 5 years ago when I need to maintain a big SaaS rails codebase, and in order to support the increasing quantity of users, I need to throw more powerful and expensive machines, and it was hurting us at that time, and after some POCs, we perceived that it would be really interesting to rewrite some parts of our application in Elixir with Phoenix. I think that it's an important tool to have at hand, something that you can reach if needed.
I wouldn't say it's limiting in the sense you can't create certain things with it. You just need to be very prepared to maybe make more choices and also write a lot more libraries that you could potentially find in Python or Ruby.
It also depends on the app you're building. For me I was building a very large app (a video course platform with multiple payment gateways). One limitation I came across with Elixir is there's no official SDKs for Stripe, PayPal, Braintree or Paddle but there are SDKs for most other popular languages. So if you plan to interface with a number of APIs, chances are you're not going to find an official client for Elixir unless the company happens to be using Elixir or are happy to support it (such as Mux).
It could be challenging and time consuming to have to write both your app level features and the underlying libraries. If your goal is to get a web app launched quickly to test it out and you already have experience with Python, Ruby, Node or PHP it's kind of a hard sell to use Elixir. It's mainly because other languages have way more community libraries and frameworks available that cover common web feature use cases. Plus there's a lot more community resources around blog posts, videos, books, courses, etc..
There's also an interesting divide right now in Phoenix around using Live View or not and if you go down the LV route there's very few resources beyond the docs, especially now with LV 0.16 coming out which completely changed the templating system and how components work. It still feels like it's in a pre-1.0 (because it is :D) semi-experimental state. As far as I know there's also no really big success stories with LV. I don't know of any big sites who are using it all-in to drive the entire navigation of their site and all routes.
The above continues to fall in line with my overall feeling of having choice fatigue with Elixir.
With that said if you're interested in it, maybe try to put together a proof concept that focuses on the hardest part of your app and if it works, make a judgment call based on your personal experience. It's possible you'll have better luck than I did. Programming language selection is a very personal choice, especially when you get past libraries choices and start writing code. If Elixir clicks enough for you at a fundamental level maybe it'll be a better choice even if it means having to write more libraries.
No. I'd say even if you don't end up using it in your day to day, learning elixir/Erlang and reading Armstrong's thesis are some of the best things you can do for yourself in terms of "system design/programming enlightenment".
It's just not fun to be in a constant state of package fatigue, especially when a lot of semi-popular libraries are maintained by 1 person. If that 1 person leaves that entire bit of functionality becomes a liability to your application because it's unrealistically demanding to be a solo developer or small team and be responsible to maintain a bunch of libraries that become unmaintained but then also build your application.
This is IMO especially true with a language as powerful as Elixir with macros. Picking up and reading someone else's code can either feel natural or be really hard, to the point where looking at it doesn't feel like the language you know. This makes it doubly hard to read 3rd party library code because you're learning the other person's code and have to mentally deconstruct a lot of advanced patterns if they use them. I don't consider myself that good of a programmer but there's a lot of times where in Elixir, phrases like "this is impossible for me to understand" come up when I've written hundreds of thousands of lines of code in Python but never thought this. I sometimes had the "what am I looking at?" feeling with Ruby too btw.
As for library availability, this is a problem that doesn't come up as often with more main stream web frameworks, at least not in the Python and Ruby eco-system. Sure things go in and out of fashion but both languages have frameworks that include more batteries included or the community has gotten so big that there's a bunch of independently developed libraries that most of the community got behind and supports it so well that it becomes a no-brainer to use it.
So that's what keeps me on the fence and I think some of these problems can be solved with time, but time is a scary thing because waiting a few years feels like an eternity and the outcome after waiting a few years might be waiting a few more years. At some point you need to build whatever you're building and run with it without looking back.
But I think this really comes down to personal preference. I used to think I wanted unlimited choice and an endless world of possibilities. I don't. I want to build web applications quickly using the most straight forward code I can think of and get as many batteries as included as possible while leaning on / contributing back to a massive eco-system. I don't want to be on the front lines of building a new eco-system. I still do think in the very long term (5+ years maybe) Elixir could be a good match for me once there's a lot of libraries that have hit critical mass.
There's plenty of people using it successfully now, and I'm happy there are people who like being closer to early adopters and setting up the initial ground work for an eco-system.