I do think it is "just" a matter of time/momentum. There's definitely a lot of cargo culting around bundlers ("these bundlers were gifted to us from the gods!", "these were my father's bundlers, I simply must use them!") and there's a lot of developers who "love" scaffolding and boiler plate that are just going to blindly do whatever `create-react-app` or `ng new` or whatever scaffolder of the day briefly masticates then vomits out for their baby bird mouths. Those things (culture, scaffolders) all move slowly (for lots of good reasons, too) and just take time and a few revolutionaries.

HTTP/1 still isn't going anywhere, anytime soon, especially in developer tools (because for better and worse HTTP/2+ requires TLS and developer tools are tougher to build with TLS), so it's still hard to combat the cultural assertions that "bundlers are best practice" and "bundlers are required for performance". But that too is something that shifts slowly over time. There are decades of momentum behind HTTP/1.x.

There's also still so much momentum behind frameworks like React, Angular, plenty more that spent so much time in CommonJS that they still haven't yet sorted out their ESM builds. That's also something getting better with time. Especially now that Node LTS covers enough that you can take an "ESM ONLY (in Node)" approach with confidence.

As I mentioned, I've had the pleasure of working with some projects that were 100% unbundled ESM in development and then spot-bundled (often with esbuild) to highly specific sub-bundles just for Production where Production performance noted improvements. The world of ESM-first is nice when you give it a chance. It will take a bit longer to get to "ESM ONLY, EVERY WHERE", but it still seems to be a matter of time/momentum rather than a problem with ESM.