I get the impression making a web app was considerably more difficult for a solo developer pre-jQuery. For a while we had an explosion of choices, and ultimately things coalesced around React and similar paradigms. Meanwhile the per-capita productivity has been skyrocketing as increasingly sophisticated cloud services provide everything from raw key-value storage to turnkey caching and auth solutions.

Is it more complex than single-device programming? Perhaps, but the modern browsers represent a nearly universal platform with very low per-user complexity.