I think we have far more that we agree on in this conversation than we disagree on. We can get into the minutiae of specific UIs but that probably misses the point.
Where I agree with OP is on the first impression of the default Lemmy UI to users trying to migrate from big-corpo products
For better or worse, these folks have come to believe that "slick looking" = thoughtfully designed = featureful and advanced. And that "sterile/boring looking" = amateur UX design = complicated and difficult
We can't break that mentality in the general public by simply repeating over and over that they're wrong. It just doesn't work that way, sadly.
On my Mastodon server, we have the Elk frontend available and have it listed prominently right next to the sign-up/sign-in button as a "Twitter-friendly UI experience" (also on our About page). Then, we periodically throw up an announcement telling users that apps, Elk, etc don't provide all of the features available on the modified webUI/PWA, along with a list of what they're missing and how to learn more.
It's an "abopt, extend, extinguish" approach and it works. There's a reason corporate enshitification pioneered that strategy. We can use it too, but for good :)
User instance checks out