Semi related, is there any sort of service or type of professional that does mentoring/handholding of someone who has the core code that does something but who won't/can't take the steps on their own to make it a service or app they could sell?
Yeah to be more specific I mean I'm sure I'm not unique, there's a whole class of people who can create something easily but who don't have the personality or wherewithal or desire to sell it or pretend it could be a unicorn or seek out a formal co-founder.
But who'd be happier tending to the day to day of keeping their own service growing and running well than other kinds of employment.
The problem is that unless you have something very valuable and hard to replicate - which is by far the exception - any businessperson who's willing to do all the work of bringing something to market can typically hire developers to implement it for them, and be in total control of the product, instead of depending on someone whose motivations don't align with the business they're building.
In short, there's nothing in it for them except a hard to manage risk.