Tumblr has made a lot of… questionable UX decisions, but the users have found ways around them.
Something I forgot to mention as a possible origin for putting text in tags: Tumblr used to allow you to edit other peoples’ posts when you reblogged them, leading to a fear of Danny Devito and, infamously, the John Green post.
@TrickDacy@lemmy.world important addendum
I avoided it for a while because it felt so clunky, but it has really improved in the last decade.