Paul Buchheit says that people at the leading edge of a rapidly changing field "live in the future." Combine that with Pirsig and you get: Live in the future, then build what's missing. That describes the way many if not most of the biggest startups got started. — How to Get Startup Ideas by Paul Graham.
These aren't necessarily "startup ideas"—just stuff I wish someone would build. Feel free take one and run with it; I'll be your first customer.
Oster for information security. Frustrated with the state of pregnancy and parenting advie, Emily Oster wrote Expecting Better and Cribsheet. An expectant mother who's also an economics professor, she takes readers on a tour of the medical science (peer-reviewed scientific literature), explaining not just what's known/uncertain, but crucially, why.
I wish someone would do this for information security—a book for nonspecialists, explaining how individuals and non-technology business owners can improve their security postures. A good version of this would explain "the ten things you should do", ranked using cost/benefit analysis, with as much epistemic rigor as possible.
Payments and accounting for lumpy payers. Professional services firms, wholesalers, and landlords typically receive big payments from a few repeat customers. These domains have hung on to paper checks for a few reasons: (1) little to no direct cost (other than check stock), (2) anyone with a bank account can write and receive checks, and (3) parties transact repeatedly in a long-term relationship with real and ongoing credit risk, so avoiding bounces isn't the big concern. Even so, checks are awful; they're slow, get lost, there's no way to track their status, and it's up to payers to get the address and amounts right.
A better approach would move the whole thing online, integrate accounting and payment processing, and offer a payment mechanism similar to ACH but without the hassle. Zelle might be a good foundation, but they work only with banks (no API). Cozy is a promising example for mom and pop landlords. When I had to collect payments like this, I used Xero for accounting and bill.com for payment processing; it didn't work very well.
Electrification specialists. Decarbonization requires moving a lot of stuff formerly powered with hydrocarbons (cars, HVAC, cooking) to electric power. Contractors largely lack the cross-functional design expertise required for re-engineering of this magnitude, and GCs don't want thousands of tiny projects with fussy homeowners. The solution will be some kind of blended retailer/installer (a "Geek Squad" of decarbonization), augmented by sophisticated project management and design software to lay everything out, control costs, and deal with permitting.