Speaking from ignorance or speaking from ego or both? There's only three major players, React, Vue or Angular. Angular is batteries included. The other two have their lib ecosystem and if not you can easily wrap stuff around regular js libs. That's about it. The JS ecosystem sees many newcomers, it's only natural that some of the codebases were written poorly or that the FOTM mentality gets a lot of steam, against proper engineering principles.

Anecdotally the worst code I've ever seen was in a PHP codebase, which to me, would be the predecessor of JavaScript in this regard, bolstering many junior programmers maintaining legacy (or writing Greenfield ) systems due to cheap businesses being cheap. Anyways, thousands long LoC files, with broken indentation and newlines, interspersed JS and CSS here and there. Truly madness, but that's another story. Point is JavaScript is JavaScript, and other fields like systems and backend, mainly backend, act conceited and talk about JS as if it was the devil, when things like C++, Java, aren't necessarily known for having pretty codebases.