[mrj]

It depends who you want to work for. C# and Windows tend to be more popular with a certain type of company, often one more established.

The node/react world tends to be more popular with younger companies and startups.

You'll find overlap in these worlds but it is a hard road to go against the overall direction of a market. It'll limit opportunities but can be done. It's up to you to figure out which is more suitable. But it's not a dead-end. If you're looking around and noticing your peers aren't into the same things you are, you may be trying to go against the direction of the market. You could try changing your peers.