CVS was the best option when SourceForge began, and Subversion was barely an improvement. SourceForce was critical to the growth of Open Source and Free Software in the 00s. Projects no longer needed to maintain their own revision control server, file server, forum, issue tracker, etc. SF.net wasn't great compared to any of the current generation of hosting services. And, most Open Source projects were in an uncomfortable state of looking around for alternatives by the time Github arrived in 2008, because it was slow to adopt newer technologies and was running on a skeleton crew. Most of my projects had their own forums/issue trackers, and were self-hosting git, by then. Ads stopped being a usable revenue strategy, so SF.net stopped being able to keep up with what developers wanted.

But, it had a few years where every OSS developer I knew had nothing but positive feelings toward SourceForge. It gave one of the projects I work on thousands of dollars worth of transit over the years. It's hard for folks who've only ever worked on an "everything for small developers is a loss leader" internet to understand that we used to pay for and manage our own servers. I had a $200/month bill for just my Open Source projects on a couple of colocated servers.

Yes, SourceForge went through a lot of shitty stuff. The overtly hostile stuff (adware inserted in OSS projects) happened after it changed hands. But, when the revenue of their original model dried up and they couldn't stay on top of new development (being slow to offer a good git experience was a fatal mistake).

Anyway, it's not great now (though it is now owned by seemingly decent folks, who haven't really been able to find a way to make it work), and it went through a period where it was a borderline criminal enterprise, but it started out as a genuinely helpful part of the OSS community.