Overreliance on SPAs.
Software that works fine on the developer’s 6-month-old high end workstation and like molasses anywhere else.
The subscription model for EVERYTHING.
Also: software that works like molasses on the developer's high end workstation
A part of me still kinda wishes Microsoft (or some other single big vendor) won out and standardized a set of common APIs/UIs/SDKs, like .NET with WPF or something, rather than the hodgepodge that is the modern web. On one hand it's cool that it's a relatively open ecosystem (vs, say, the mobile app stores), but my god, does the dev ex and UX suffer from the fragmentation. And it's not like modern web apps are really any substantially better than 90s desktop app.
I'm a frontend dev who occasionally hears this complaint from certain users. If there were some way to be more accommodating to them, I'd love to learn! For example, some people hate the "modern" use of a lot of whitespace with less text density, or mobile menus on desktop (I hate that too), etc.
I don't think any UX designer sets out to purposely try to overcomplicate things, but there are good designers and bad designers out there, and also, most of them are young and don't have the lived experience of older computer users and don't remember older UIs. I would love to share comments and tips with them if I knew what the specific issues were.