This may be a gross oversimplification, but I think the point approximately stands. As soon as a niche with high problem density is discovered, the density of skilled problem-solvers in that area quickly rises to meet it. You can only stand out if (a) you’re an early adopter, (b) you have skills that others in your area would find it prohibitively difficult to replicate, or (c) your niche isn’t too fruitful—i.e. nobody is interested in trying to rake in a share of the profit.
This was a good crystallization of this point, thanks.
This was a good crystallization of this point, thanks.