There are hundreds of thousands, if not millions of people building small businesses to leverage a tiny opportunity in the market. Build a feature that no major player has captured yet.
This is good for the user for a time. But then they end up with a ton of tiny subscriptions, and trying to link them together to make a complete product. All these tiny companies competing for eyeballs, to get the marketing to be recognized on top of the other tiny companies building similar tools.
And what's the goal of almost all of these little tools? To make a small difference in the efficiency of somebody running their business. Minor efficiencies, not game changers for the most part.
Then one of the big players comes in and adds the feature to their main product. Poof, everything somebody worked long and hard for disappears.
Niche to find what you can build that's larger, but I think staying niche as a goal is a challenge.