I haven’t worked with web apps that need highly interactive frontends, but for our e-commerce stores and internal rails apps turbo and stimulus have really lowered the bar on how much new developers must learn to build a nice to use website.
Most of the complexity, especially the UI part, has been self-inflicted. The old ways are very much not outdated, and are actually coming back.
There is a whole young generation of devs who came into the job at the stupidest possible time, when the industry convinced them that every web application has to be an overcomplicated, insufferable mess.