You can still deploy stuff on a plain application server or whatever. The tools I've worked with haven't really required touching any kind of cluster management

You can still deploy stuff on a plain application server or whatever. The tools I've worked with haven't really required touching any kind of cluster management or other overhyped (albeit in some cases necessary) and complicated backend stuff if you didn't want to. (My backend experience is with Java and Python, though. I don't know how things are with other backend languages.) When I started looking into putting together a simple but modern frontend in my own time after having done only backend for years, it seemed like there's quite a lot of tooling and associated complexity that you kind of have to deal with just to get your frontend deployed, whether you need a complex architecture or not.