I think that the current downvote system is far from ideal, and ideally there should have some piece of “forced” feedback when you downvote someone, but keep in mind that a downvote is just “this should be less visible”. For example, people often downvote OK answers because an even better answer popped up, and they want the later to rise to the top. So a lot of times there’s no actual hostility in the downvotes.
And for other Reddit behaviours that people often call toxic (I call them SNOO - stupid, noisy, obnoxious, obtuse), I think that it’s cultural. The Reddit admins bred that behaviour into the users; and users are likely to carry it with them elsewhere, including Lemmy. I think that most of those individuals will get better over time here, and the ones who don’t will end leaving.