First I've heard of Deno Fresh! I think any SSR solution comes with the same fundamental problem, which is that for apps of sufficient complexity, you will probably want to enable interactions (e.g. liking a cast) that mutate the state without refreshing the whole page. That's where the complexity comes in.
(In addition to things like the server-side environment not having access to the same runtime variables as the client)
That’s why I love Phoenix LiveView but you guys are all TypeScript :)