So how do you know you're not missing out, or more precisely, that you're not missing out and what you are missing out is so great that the productivity you gain from restricting yourself to the subset of tools you fully master does not compensate for what you are missing out - I am thinking of frameworks like Angular or React? I am asking that as someone who doesn't use the frameworks I mentioned and sticks with vanilla JS and DOM APIs.
If you were at Google I suppose that you had lots of technical conversations with colleagues so you more or less knew about the latest trends and their benefits, but it's harder at a smaller company or working on your own.
That's the question everyone asks, right? People tend to be really insecure about the possibility that someone else might be doing better than they are.
The short answer is that you don't - there is always the possibility that someone has invented something that lets someone else do your job way more effectively. But you accept the risk that you're missing out for the certainty that you're getting features done and code written quickly. And periodically, maybe look around and try some of the new inventions that seem to be getting traction to see if they really do make your job better.
The key point is to rely on your own data and observations rather than the opinions of others.
Anybody who adopted Angular right out of the gate is kicking themselves now because everything they wrote in the last year is now obsolete. Hopping on the latest thing might be fun and you might learn a few things, but I'd prefer to wait for things to be fully battle tested and have a good history of support before I put it into production.
Another good reason is speed. It's rare for a framework to be faster than native DOM api's. And the app loads faster!
If you were at Google I suppose that you had lots of technical conversations with colleagues so you more or less knew about the latest trends and their benefits, but it's harder at a smaller company or working on your own.