I'm still a big fan of the developer experience Vue provides and I'm locked into a framework for my work projects so I won't be switching those over any time soon, but I've been meaning to try out Svelte for a personal project some time.
No longer the case. Vue 3 was written to have a "compiler-informed Virtual DOM"; there are a bunch of videos about it on YouTube if you're interested.
How does this scale to anything remotely complex?
I've found that if you have a decent knowledge of React it's hard to make anything slow with it.
https://stefankrause.net/js-frameworks-benchmark8/table.html
And Svelte is fast. It's as fast or faster than React in most synthetic benchmarks.
For how and why, see https://svelte.dev/blog/virtual-dom-is-pure-overhead (notably the intelligent compilation step which removes need for vdom)
However the issue with both svelte and stencil is their lack of ecosystem, even if they have interop with webcomponents, today the market is too small.