Also scoped registry has been proposed like 3 years ago and still pending. This would allow multiple versions of the components to cohexist in the same document. There are tweaks but then styling would only work with shadowDOM.
I want web components with slots, lightDOM (no shadow) and css modules.

Hydration causes flickering when you apply styles conditionally via js to big elements. The worst part of web components is that you lose slots if you don't use shadowDOM, and then composition is very limited. Everything works with buttons and badges, but with tables and dropdowns is a bit different

I was a huge advocate for building design systems with web components, until components got complex. Shadow DOM was complicating things around, we suddently needed portals, testing libraries were not being able to access shadowed parts of the components.