I think you hit the nail on the head here. The designers that have worked on my site seem to be focused on screens that they can add to their Dribble portfolio rather than getting the job done in an efficient way for my users.
Meanwhile lots of successful sites don’t follow design trends the way every designer and startup seem to want to, and others do spend a lot of money fucking up their UI but not in a trendy or attractive way, particularly, and are successful nonetheless.
I suspect “minimum viable design” is much cheaper and more straightforward than a lot of what’s being treated as necessary to attract users, and has less to do with following trends or cute animations or whatever than simply appearing to have been updated some time later than 2005.
This adds cost and worsens UX. It has less to do with making the app look attractive from the user’s perspective than with designer ego and satisfying the brand-over-all-other-concerns product owner types. Usually there’s little discussion of features that will be missed so the widgets can work worse, but design flair should, properly, be part of the discussion of what your velocity may look like.
[edit] I suspect some of the motivation for designers here is a combo of selling designs to clients or product owners, who are easily flattered that they need this kind of thing, and their version of résumé-driven-development—that is, highly-custom trendy screenshots probably “pop” a lot better in a portfolio than a better-functioning app that looks more ordinary.