In uBlock Origin settings > My filters, paste the following rules to turn YouTube in just a search bar + video player:

  youtube.com##ytd-browse[page-subtype='home']
  youtube.com##ytd-watch-next-secondary-results-renderer
  youtube.com##app-drawer
  youtube.com##ytd-item-section-renderer.ytd-comments
  youtube.com##ytd-guide-renderer
  youtube.com##ytd-mini-guide-renderer
  youtube.com##ytd-topbar-menu-button-renderer
  youtube.com###buttons.ytd-masthead
  youtube.com##yt-icon-button
  youtube.com##.ytp-endscreen-content

Note this is only accurate at the time of writing, only works partially on mobile, and may break some edge cases I don't use :)

[1]: https://github.com/gorhill/uBlock/wiki/Static-filter-syntax