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.
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.