Codeberg only services free and open source projects
There are other limitatiosns:
They don't provide a free, well designed and isolated CI like GitHub does
The space of Packages/Registry is limited
As it's quite niche there are a lot less people on that platform in general
Although GitHub is under fire for their uptime: The uptime of Codeberg is quite comparable to GitHub, when having a look at the functionality that both platforms have in common.
Regarding self-hosting:
Too expensive / time intensive for most devs that just want to code
Needs like 100MB RAM to run, so it can basically run on almost anything. If you like some extra security: Do another layer of authentication in the reverse proxy that faces the internet.
Let me guess the same BS as with Oracle: "We need more money for AI so that's why we brain drain our company by firing everyone who is too expensive (except the CEO)"