When I was on Windows 10 still, I used Open Shell for the start menu, and much like you, Retrobar for the taskbar. But I hear on Windows 11, it comes into conflict with Retrobar. I also used AIMP as an audio player. I went back to it after the dev said he was beta testing better compatibility with Linux. There's a bunch of themes for it in different styles. This includes themes that look like older versions of Windows Media Player, but also various other things like ones themed after real life devices. I also tried Wacup for a bit which is an up to date version of Winamp.
You can also use client mods for certain programs like Vencord (Discord), Aerochat (Discord) or Spicetify (Spotify) to apply themes to them. If you use Spicetify, I recommend the WMPotify theme since it's the only skeuomorphic theme.
I've also seen some people use Escargot as a way of using Windows Live Messenger with their outlook account.