You already know the value of a niche - you go up in market value the more specialized you are in anything. So what do you specialize in?
There are many schools of thought, including ones where you could be a generalist that doesn't specialize in anything. I find one rule to be simplest and most effective above all: Specialize in the New.
Didn't we just agree to avoid FOMO? Well yes, thats an important distinction - don't specialize in everything new. Specializing means you have to say no to a lot of things. Just pick something new that fascinates you, and hopefully many others as well. Since you're learning in public, you'll know when you hit on a real nerve. Budget in the idea that you'll fail a few times before you find Your Thing.
Then the other big objection: There are plenty of jobs/money/etc in (fill in the blank older technology) too! This is usually followed by some big numbers and anecdata. "My brother's cousin's roommate's friend took this COBOL job and now he's ear