Edit: 2001, I see one (1) banner ad, and that ad was seemingly for an OSDN (Open Source Developer Network) conference. https://web.archive.org/web/20010517002942/http://sourceforg...
Given SourceForge only hosted Open Source software, and had no source of revenue beyond ads and sponsors for quite a long time, AFAIR, I think they get a pass on a banner ad.
(My SF account dates from June 2004. I expect I was thinking about using it as version control for a FOSS project I was working on at the time, though I don't know why, as it seems SF didn't support svn until 2005. Maybe I couldn't find any better options? The pre-GitHub ecosystem was pretty bad! But, luckily, I ended up not having time for any FOSS stuff from about autumn 2004, so: problem solved. And when I next looked, in early 2010, everything seemed to be git+github, and all the better for it.)
No, as others have said it wasn't always that way. And more importantly it's not that way now. But yes, for a while there it was the epitome of enshittication. How that worked out is kinda hopeful in a way: it went broke, was bought out, and went back to being something usable again. In fact they added a lot of enhancements.
I know because I was one of the ones that went back to it. I didn't like having git being forced down my throat, and sourceforge was one of the few left that supports a whole pile of VCSs. I made my Makefiles [0] support it so I didn't need to deal with the UI, and ended up very happy.
Everyone wondered why I wasn't on github, and queried my sanity at the time. But I say not liking the git cli is perfectly sane. Now jj has come along that excuse has gone, but it was a good one at the time. "github sucks" has conveniently come along as a reason to stay on sourceforge.
Seriously, if you are considering ditching github, take a look at sourceforge. The current owners BizX deserve some reward for the time they've put into it, and their patience.
[0] https://sourceforge.net/p/http-proxy-tunnel/code/ci/default/...
