I like the new purple in the sidebar. But I think the hard borders around the bottom and top navs, search, buttons, plus around the top right menu that comes out from the avatar need to go. The softer lines used for the light theme are just fine, and should be used in dark mode as well.
If you look at how other big sites use dark mode (Github, Gmail) they rely on softer lines and shades, not high contrast, which just ends up hurting people’s eyes and defeats the purpose.