A couple uBO filter rules, paste it to the "My filters" tab on the settings:

    ! Nuke high contrast elements
    www.youtube.com##ytd-feed-filter-chip-bar-renderer
    www.youtube.com##yt-chip-cloud-renderer

    ! Nuke news sections and other "engagement boosting" sections of the homepage
    ! This breaks the channel page, I temporary disable the filter rules when I need to go in there. Selector can probably be refined
    www.youtube.com##ytd-rich-section-renderer

    ! Nuke Shorts
    www.youtube.com##[is-slim-media]

I also have a couple fixes on https://userstyles.world/style/6382/my-youtube-fixes which you can apply using the Stylus addon, these compact the layout a bit more, lowers contrast of "calls to action" like the Subscribe or comment buttons, as well as attempts to make the Theater view actually take all of the available screen space (without being actually fullscreen).