Well you can't really. If you want to write frontend apps, for example, you have to use JS. You could technically use some FPLang-to-JS compiler, but those suck more often than not.

Also, I don't see how "let's not make a thing better just because it was not meant to work this way" is an argument.

I'm sure there is a fallacy name for this, but consider some other examples: "You could always use fridges for cooling and let cars be" or "You could always use computers for browsing the internet and leave phones be".