I challenge anyone who believes "the complexity building websites is growing" to go ahead and build a web app relying on multiple complex state machines with imperative jQuery calls, and then tell me it's less complex than the equivalent in React.
If I can't just include a file things are going to get more complex.
State machines are a method to solve a problem that could be expressed in other ways to make it fit the language better.
If I want to implement a rich text editor in my website, it will be as easy as 'npm install ...' and an import statement in the relevant file.
Is there an advantage to make a state machine to solve this?
But the tooling and npm packages are all optional. You can import React from a CDN and use stuff like htm [1] or domz [2] instead of a JSX compilation step.
Or you can use Vue instead of React (their tutorial starts by using Vue via CDN).
If you're able to only support 95% of the browsers, you can use most modern ES6 features, including ES Modules and async/await.
If you still need the tooling, there are options like Parcel [3] or Poi.js [4] that require zero configuration. You don't really need the complexity of Webpack.
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[1] https://www.npmjs.com/package/htm
[2] https://www.npmjs.com/package/domz
When I tried to include other packages they were only available through npm (some had cdn versions but most did not). You don't get access to the entire ecosystem without the tooling.