All of those things are intimately connected. If jQuery were just as fast to work with and had the same bug count, it wouldn't be harder to maintain. It takes

All of those things are intimately connected. If jQuery were just as fast to work with and had the same bug count, it wouldn't be harder to maintain. It takes time to work out what jQuery code is doing which means it takes longer to modify the code. That difference in readability also leads to a higher chance of bugs due to misunderstanding something. The one case where this does not hold true is when your site only needs a few click handlers or something else that is simple (and in those cases, you should probably be using jQuery -- or just the normal DOM now that compatibility is less of an issue). But that is not what modern JS app devs deal with. The entire reason for using Handlebars on top of jQuery was to move toward declarative programming in order to reduce bugs and speed up development time. React was more declarative, functional, and native (use JS builtins instead of embedding a turing-complete DSL) along with also being massively faster. React was marketed more on performance than anything else at first, but that was mostly because Handlebars and backbone had already solved the worst parts of jQuery in large codebases -- procedural UI and holding state in the DOM.