I like React because these days it's pretty well known and just about anything I need I can find easily. There's newer similar tools like Vue, or entirely different approaches like Next, but React remains a dominant choice for the time being. I'm sure fashion will move the industry along soon enough, but none of the newer tools I've seen really are such a huge leap forward that I couldn't get stuff done in a few days of prep and tutorials. So for now, I'll stick with react until I need to move or a client requests it.

For backend I'm increasingly preferring simple Restful APIs. If it can map an endpoint to a function and convert JSON into a dictionary or object, it's probably good enough. I just wrapped up a project in ASP.Net Core and that pretty much just got out of the way and let me make web API endpoints.