What killed Reddit wasn't just its corporate chase for profit. It was also the fact that the general public's default internet device shifted to the smartphone and its limited keyboard and screen, no longer the computer. That led to comments largely being reduced to 140-character quips, no longer substantial discussion.
I am skeptical any non-corporate replacement like Lemmy can bring the old internet feeling back, because even on those alternative platforms, you just won't get many people using computers again.
Reddit ended up gamifying for engagement/rage-bait instead of natural, authentic discussion.
It also was because it became a target to influence and manipulate people both by every day scammers and marketers as well as nation state level actors.