I'd say SourceForge was abandoned due to VA Linux going under. I remember the pain/panic as large numbers of OSS projects were suddenly scrambling to find alternatives to SF. I actually started a subscription to GitHub just to try and help ensure they had the money to stay in business, and we didn't have to go thru that again.
People have a superficial knowledge of the space (I think this extends beyond Codeberg) but feel strongly that they need to advocate for something. Codeberg themselves seem to have opinions about what they want to do but people are suggesting they can do more simply because it gives them an outlet.
The constraints that Codeberg set seem to, on the surface at least, ensure they can scale based on their needs and protect them from external threats. Hosting random sites comes with a range of liabilities they probably understand and want to avoid right now. There are EU regulations which can be challenging to handle.