Here's what I added to uBlock:

  ! YouTube
  ! Remove blue box
  www.youtube.com###clarify-box
  ! Remove shorts
  www.youtube.com##ytd-rich-section-renderer.ytd-rich-grid-renderer.style-scope:has(#rich-shelf-header:has-text(Shorts))
  www.youtube.com##ytd-reel-shelf-renderer.ytd-item-section-renderer.style-scope:has(h2.ytd-reel-shelf-renderer.style-scope:has-text(Shorts))