The problem is a "Reddit alternative" will naturally attract the groups that no longer feel at home on Reddit. It seems inevitable that any alternative will be more toxic and/or hyper-moderated.
As will almost any site specifically marketed as an alternative to a major one. You market your site as a freer, more fair alternative to another social site, and yes, you'll likely draw in the people that were hated/seen as controversial on the original. See also a lot of Twitter alternatives (like Gab) if you want other examples.