New user here, just got invited and started poking around the site, and the thing that most stands out to me is the bright white theme of the site.
Its a big trend that most sites seem to not be catching onto, users want a dark theme at least as an option, because the blinding white webpages at this point almost seem dated, and if you're browsing at night/in a not very well lit room, they come off as harsh, sometimes almost blinding. You can see the demand for this being fulfilled with plugins on most sites, as the websites themselves seem to be slow to act. YouTube for instance is terrible with its default white scheme, but pretty nice if you do the "secret" dark theme. Slack too, although I use a plugin for that, same with Reddit and using RES to turn on a dark theme.
So while I know the list of things to do is probably a mile long, a dark theme would go a long way to making the site more appealing I think, and give it an edge as a more "modern" website.