Sure, but there's something in between of huge sites like 4chan/YouTube/Facebook and these dead altchans everywhere.
You could roll at least a dozen of these altchans together into one site yet they're competing against each other for their two posts per day. I mean just looking at this thread (and the many many deleted threads for advertisement) shows you that there's probably like 5 new altchans per year. All are totally NOT like 4chan :^) but don't have any identity besides trying hard not to be like 4chan but if you care enough to check the sites out you'll see that many are just 4chan in slow motion so you can REALLY observe shit as it hits the toilet bowl.
Then there's the ones that painstakingly try to emulate 2006 but always fail.
Idk, I've been hopping alt chans for over a decade now and the only ones that really flourish(ed) are/were national chans like sosach, kc, dejimachan, ernst, britfa.gs, yli, brchan etc. and the very early 4chan alternatives like 7chan or 420chan. All those managed to emancipate from their parent and develop their own culture while building a reasonable size of a userbase. Far from 4chan's highspeed but also well over deadaltchan#9001.