The key is that maintenance is done on your own terms, and thus it's available when you need it.

You can run it in an HA configuration with multiple servers and live updates.

Yes. And the same for the database and then you get it into “professional” territories with more moving parts that can also fail and take 3 hours to figure it out and recover.

Yup. It's kinda binary: either almost no downtime for years with a crazy number of nines, or a total mess for several days while people figure out the issues.

That being said, a Git forge for a small/mid-sized company is not something that requires rocket surgery. Forgejo with an SQLite database and a daily backup to S3 would be more than enough for the majority of users.