[danielvaughn]

One of the problems with native encapsulation is that UI frameworks almost never fully satisfy the product requirements for a given application, so in some cases it’s always necessary to override either behavior or styling. If you remove that capability with a shadow DOM, you damn well better be sure that your abstraction is perfect.

[Keithamus]

That’s what CSS parts and slots are for. Your component can style its own boundaries, provide parts to allow customisation, and use slots to inject components that are styled from outside (be it another ShadowDOM or the light DOM)

[danielvaughn]

Yep, though what I’m getting at is that those slots/parts better give you near-infinite flexibility. Because if you encounter a scenario where the slots don’t provide what you need, then you’re screwed.

Source: I fought with Ionic code for months over this. Really soured me on native encapsulation, but I see the benefits still. I just think it has to be approved very very very carefully.