Modern FE is a discipline every bit as complex as anything that we face in the backend. It requires that we actually apply an architecture. Design our code so that we can respond to changes in our business requirements etc. Serious engineering rigor in other words. Hell I could make the argument that in some ways backend dev is much more straightforward.
I think it’s fair to say that we often put too much business logic into the front end. Fat clients are not something I agree with. But to say things used to be better is just flat out incorrect.