I learned Javascript was made for making the web interactive. I choose to use it this way. There's nothing wrong with using it for backends too, I just prefer using other langs for that domain as it just doesn't feel right to build my backend in Js/Ts.

For small and moderate projects I dont see issues, but I always build with scaling in mind and I'd like to keep the bill for that small.

TypeScript is a wildly unpleasant language. If I'm going to be waiting around for a compiler anyway, why not use an easier nominally typed language? I mean, dotnet is right there... and it's got features out of the wazoo. No need to download external libraries when your bloated backend framework ties your shoes for you.

Or if I'm really into structural typing, Go is right there. I'll tell you, it compiles a lot faster. And a lot less type Olympics, too. Easier to read. Less bug-prone. TS isn't a bad language. But it's certainly not the best.