Was it, though?
Sure, I'm not going to minimize the benefits of discoverability, avoiding the need for users to create yet another account, and taking the burden of infra maintenance off of someone who'd otherwise have to stand up a server to host phpBB or whatever.
But ultimately we don't strictly need these things. Isolated/fragmented web forums were doing just fine before Reddit came along. Maybe adding a little friction to the process of a first post to a new forum is a feature, not a bug.
> Reddit had a good thing, but neglect and mismanagement ruined it.
Yes and no. Ultimately, any time you hitch your community to someone else's platform, you incur the large risk that the platform owners will make changes that you don't like. It's not even "neglect and mismanagement": Reddit's owners have been doing what they believe increases the value of Reddit. Whether they're wrong or right about what changes accomplish that ultimately doesn't matter: those changes might not be what makes users and moderators happy, and users and moderators don't have much power to affect change. This protest/blackout may end up achieving the desired effect, but think of the time, energy, and effort wasted around all of it. Better to spend that time working on solutions that allow communities to own their slice of the platform, and have final say as to what happens with it.