Different people, different taste.
I love FairEmail because of its "millions" of settings and the privacy features, for an example if you press a link, you'll get a popup with options (for an example, what app you want to open the link with). And if the link contains trackers, FairEmail will remove these by default and saying "tracking parameters removed" with yellow text in bold.
K-9 Mail feels incomplete in comparison. Have you tried FairEmail?
Like what another person said, hate is a strong word. But when it comes to Big Tech, I'm all for the word.
Might have missed adding something to the list. Will add more if I have.