I think a lot of people assume this is the case for every website/web application without actually watching their network requests and having hard data on it. Like I said, small to medium sites and applications in some cases start to be more efficient with ESM modules than ever before (because it is the ultimate code-splitting) even before you get into new tools like HTTP2 and HTTP3 which significantly reduce connection overhead for network requests entirely and make a lot of old bundling advice outdated at best.

Plus, ESM modules always load asynchronously without DOM blocking so in any and all "progressive enhanced" sites and apps, it may feel slow to hydrate parts of it, but you generally aren't going to find a better performing experience while it hydrates. The page itself won't feel "slow" to the user because they can start reading/scrolling faster.

Some of it comes down to your framework, of course, and if you can afford SSR or are using a "progressive enhanced" style of site/application. For one specific counter-instance I'm aware of, Angular's NgModules dependency injection configuration mess routes around ESM's module loaders and creates giant spaghetti balls the browser thinks it needs to load all at once. I can't see recommending unbundling Angular apps any time soon as long as they continue to break the useful parts of ESM style loading with such spaghetti balls. Other frameworks, especially ones with good SSR support/progressive enhancement approaches are increasingly fine to start using unbundled ESM on the modern web.

I thought http2 made the network requests a non-issue (at least for 100 files or so). The only advantage of the larger bundle is though compression.

I didn't have much of any trouble in Snowpack with even the largest projects I worked on but at least with Snowpack it was easy enough to target "freeze" a sub-tree of modules into Snowpack's "web_modules" with esbuild. I don't know about Vite in that case as I haven't been convinced to actually try Vite despite Snowpack's shutdown endorsement. Recent stuff for me has either been projects still using webpack for platform reasons or ESM with hand-targeted esbuild bundles for specific module trees (libraries) without using Vite or Snowpack above that. About the only thing I feel I'm missing in those esbuild workflows is a good HMR dev server but the simplicity of using fewer, more targeted tools feels handy to me.