Is Svelte a good choice for large-scale apps?

Large scale is all about the back-end, not the front end. Svelte is fine for the front end of any website.

But React is more popular and if you want to actually make an app, you could consider react native and reuse a lot of your code.

There was a big discussion about Svelte recently, here’s one of many comments that may be relevant:

https://news.ycombinator.com/item?id=37380980#37382287

TLDR: Svelte is like Rails, lots of magic to do pre-ordained stuff quickly. If it can do everything you need your UI to do it will be very productive. But if you have UI requirements that don’t exist in Svelte (or Sveltekit) out of the box, you may be better served by a more primitives/toolbox-based framework like Solidjs.

Svelte bundle size supposedly grows faster than React, you may want to check out comparisons in case that's your concern.