Grapple: Ug....5e has such nice simple grapple rules, and now they are becoming more complicated again. What made grapple useful was that even though it wasn't super strong, it was fairly easy to try. Now its got more complex mechanics, bonuses and penalties, now the grappler takes the slowed condition (but only while moving, so they do or don't have enemies get advantage on attacks against them?). I get that some monsters in 5e were getting grappled way too easily, but that's because a lot of monsters that should have had athletics skill didn't. Just fix that and your golden.