Lemmy probably feels like Reddit when it first started, all warm cuddly and friendly to newcomers eager to discuss and collaborate around central topics.
I joined reddit on the tailwind, so it was all echo chamber, we hate newcomers, gatekeeping, automod frenzy, too many rulebreakers, too many rules, etc I could be wrong, but thats what I imagine it used to be like.
Honestly, the fact that Lemmy displays upvote and downvote counts (like reddit, at least with RES, used to) makes it a lot friendlier. If you say something unpopular, better to see +10/-4 than just -6 - if you're saying something unpopular but true, at least you're seeing some positive reaction.
This alone makes it worlds less toxic and less circlejerky. People won't automatically groupthink themselves into disregarding you if they realize that your comment was divisive instead of wrong.
YouTube/Google also made this mistake. Or, I'm sure it is tested to make some KPI look good. But, certainly not the ability to discern "is this video garbage/scam" at a glance.
Sure, I'm clicking more videos to find a relevant one. So, probably "increases engamement", but also reduces my willingness to pay for the service. But, I suppose it's mostly driven by ad impressions.
Haven't used Sync but I bet they carried a lot of the UI stuff over from reddit and didn't update that. Default web UI for lemmy shows the up and down.