It's tough because LiveView is really just the dessert at the Elixir dining hall-- you can't live off of dessert. It's (at least) an order of magnitude smaller an ecosystem than React and the like, and while average library quality is very high, you won't find ready-made solutions to all your use cases like you do in those big front end ecosystems. JS and LiveView do interoperate surprisingly well, so ProseMirror isn't off the table, but I still think there are important benefits in the big front-end ecosystems.
Nevermind front end though, the main course is Erlang/Elixir's concise, functional, concurrency paradigm that feels more discovered than invented. The default structures they provide for thinking about message-passing actors are so much easier than tangled webs of async functions. This means CRDTs, calling out to APIs, running jobs in other languages, realtime coms, all go very well in Elixir.
I think Actors are a paradigm shift somewhat akin to garbage collection. Increasingly complex programs demanded we abstract away memory management to stay sane, knowing we'd drop down to memory manage when needed. In this web-heavy world, we abstract into tiny statefull services (actors) to stay sane, knowing we'll drop down to sequential languages when needed.