React for 2/3 years, Vue for 1 year building large SASS apps. I use Svelte for my personal site and really enjoyed it, but dismissed it as a contender for my companies latest application. It's community is still too young, there's not enough established, battle-tested libraries for common tasks like routing. It reminds me of React in the early days, I felt overwhelmed with choice and a constant feeling the 3rd party library you are about to go all in with will be shortly replaced with a better, community backed alternative.

I'd love to re-visit that in a couple of years time when it's popularity and community has risen and is more established. Just as React did.

Mature communities are absolutely essential for any serious production development. It's doesn't matter if Svelte is technically superior in ways until it's been battle tested and has wide support.

Otherwise you'll be spending far too much time on things that other people have long ago solved in other frameworks.

While Svelte is being developed by a great programmer, it's too new, doesn't have all of it's Typescript stuff figured out, and last I checked the unit testing story was still a bit shaky. I'm guessing that in a year or less it'll get those three things figured out.

I really want to use svelte, but I don't know when it'll be production ready. From what I can tell, it's aiming to do a lot more than be a simple js framework. For now, and probably the foreseeable future, vue is good enough. Tbh, the scope for svelte is so large I really wouldn't trust it unless it got really really popular.