It’s not that odd to be good at two languages.
It’s not that odd to be good at two languages.
I think a lot of the worry comes from developers that are relatively inexperienced. We put "senior" tags on positions filled with people with only a few years of experience. Sometimes I think it's hard for newer developers to imagine what it's going to be like 10 or 20 years down the line. Being good at 2 language (or frameworks or whatever) is almost laughable. If you don't have half a dozen hanging from your belt once you've got a quarter or a third the way through your career, I think it's a big problem that you should aim to fix. Picking up something new and being effective and efficient with it very quickly is an incredibly important skill -- one which no programmer that wants to work in the field long term should avoid.
Now, if you happen to have a very young team that realistically can't handle the challenge, then that's a completely different story. It's also very important to understand what your team is capable of.
I find knowing both backend and frontend to be hugely important in the design of both systems independently.
I've been involved in tech for 2 decades now. I currently follow frontend / backend JS, Docker/Kubernetes, native mobile as well as RN and Flutter, and general DevOps. In the past I've done Office add-ons in C#, game bots in Java, PHP pre 3.0, Visual Basic GUI wayyy back in the day, done API's in Python/Ruby, and used languages I don't even remember anymore due to preexisting codebases or the team choosing something that fits better.
Back in the day we had client server architectures and it was exactly the same thing. Even more tiers would sometimes be added and there were frameworks for all of them. We didn't get source code. The frameworks were full of bugs. There was no stack overflow. Documentation usually consisted of a few trivial examples. You just had to hack, hack, hack and figure out how it worked. I remember when Swing came out and being very excited about being able to work on something that wasn't completely insane for client stuff (that's how bad it was ;-) ).
This is just the life of the computer programmer. If you like learning new things, it's never a dull moment!