SolidJS is probably the closest thing to a vanillaJS framework that you can get, in that 90% of the time it's doing the same DOM manipulations you would be doing, but with a nicer interface. So if an update causes a class to change, there's no tree to diff - that class attribute gets changed directly.

The non-Vanilla stuff is the signals implementation, which is kind of an RxJS-esque observable system, but more lightweight, and more push-based. It's very similar to Svelte, but with a React/hooks-like API (although far fewer rules to remember!) As I understand it, this system is pretty efficient, which means for simple use-cases, it's not adding much overhead over basic vanilla stuff.

The disadvantages (because there are always some) mainly come from the small ecosystem - there's not many off-the-shelf design toolkits, the documentation is a bit scratchy, etc. That community is still growing though, so that stuff will get there.