The Aria attributes can be used to block at least some of the junk, eg in ublock origin:

   twitter.com##div[aria-label="Timeline: Trending now"]
   twitter.com##aside[aria-label="Who to follow"]
   twitter.com##a[aria-label="Search and explore"]
   twitter.com##a[aria-label="Bookmarks"]

there's stuff that's no longer easy to block this way, like promoted crap in the replies to a tweet. But if that gets to be an issue, I'll just greasemonkey it. Even with obfuscated classes, the injected content is easy to identify, it's just that css doesn't let you style 'elements containing (some complicated several layers deep selector)'