It might come down to taste, but I feel like a lot of the "features" Twitch has been adding have cluttered the interface while offering little of value for someone like me who just watches streams occasionally and isn't closely involved in community events.
But most importantly, I'm bothered by the non-dismissable popups that now appear over the video feed. They seem to be for extensions, but what features they provide evades me.
These two uBlock Origin rules (which you can add in the My Filters tab) will remove the main two modals that can pop up over the video:
www.twitch.tv##.extensions-dock-card
ext-twitch.tv##.prime-extension-root
Additionally, you may want to get back a chat frame without a leaderboard header:
www.twitch.tv##.channel-leaderboard
Twitch generates random class names, possibly to prevent your blocking some elements, so I tried to find the topmost classes. I hope that's useful to some.