Just as I disagree about "full stack" developers. People that call themselves "full stack"are a backend developer that dabbles in frontend or a front end developer that can dabble on the backend. Almost never have a met a person who was equally good at both.
Just the same Languages have their strengths. Using a backend language to write your frontend is more or less a waste of developer resources. Chances are if you just chose react and typescript you could pull things off the shelf and have almost an unlimited amount of resources and developers you could pull from compared to an esoteric LiveView or webassembly type framework, get the project done faster, ship and iterate as opposed to reinventing the wheel and satisfying the commonly felt NIH syndrome.
Typescript for both frontend and backend is a bit better, but the backend story for me is still weaker than using Python or elixir, etc simply serving an API, because if you are building a company, 9 times out of 10 you are going to have to have an API anyways. I like to have the boundary of that API explicit.
the only exception to the above is if you aren't building a company and instead working on a small personal or group project.