When do you think vegetarianism started? 1990? You're ignoring thousands of years (at least) of history, bro.
Humans are omnivores. That means we have evolved to be able to eat meat, widening our available sources of sustenance. It doesn't mean we are evolved to depend on meat.
Yeah I tried Mastodon a while back and while I absolutely could have finished figuring it out, I didn't encounter anything interesting enough in my time poking around to encourage me to stay there. While the general concepts behind navigating a federated community are still kinda foreign to me, I was able to get up and running on Lemmy with much more ease and quickly start finding content that was interesting to me.