I'm also inclined, for now, to having Tree-sitter be the fast and configurable
way provider of information for font-locking, indentation, and syntactic classification.
But I confirm that LSP solves at least the first 2 of these 3 things. As to its
practicality, I'm reasonably sure that many on-line editors such as
godbolt.org,
hackerrank, etc. use LSP extensively. The font-locking is very acceptable,
even in larger files, and I'd be surprised that this font-locking is supported
by anything other than LSP.
João