The remainder is mostly gonna be regulatory arbitrage or low margin niche fields that a large company can't exploit.
The neighborhood liquor store, or the grey market handyman. That's the remaining low cap fronts.
I don't believe this. But let's assume it's true. We still have the Barksdale binary: business comes down to bundling and unbundling [1].
After the fall of the USSR the world went unipolar. The Internet was spreading and bundling was business. Now we're Balkanising. Factories and servers on one side of the planet no longer look as reliable from the other. Unbundling, now, is business.
Even if you believe the fruit has been picked, it hasn't been picked everywhere. We have a generation's work replicating Chinese dependencies in America (and vice versa), with the same applying to India and Europe.
[1] https://hbr.org/2014/06/how-to-succeed-in-business-by-bundli...
Im actually bullish on these types. I think the next wave of useful apps for people like them will be built BY them using increasingly available tools and platforms. Instead of Stanford kid making another "uber for finding plumbers" without meeting plumbers or working with them to understand their needs, some plumber with tech moderate tech skills(maybe he made wordpress sites as a kid) can hack together an AI wrapper that can tell him if everything looks up to (building) code when he uploads a video walkthrough of his work. Maybe an electrician can upload the blueprints and have AR mark every wiring run. I guess these aren't trillion dollar ideas but could still make many more millionaires.
For your plumber example, the software is the easy part. Retaining customers, managing supply chains, labor relations, managing costs , building expertise etc. is the hard part.