Curious, how would this affect the production of things that have long supply chains, or require lots of manual labor? There are many things that require labor, like plumbing, irrigation, farming, transportation, brick firing, steel production, etc. where the product is either an intermediary step, or otherwise contributes to something that the worker doesn't themself benefit from. Who would create my car, computer, desk, house, etc. if people are only working for themselves? Maybe I misunderstood your comment

>Those things would tend to be useful because at least the author found them to be and there's a decent chance they're not unique in the world. If you e.g. make an app just because you want to use it yourself, maybe someone else wants to use it too.

This seems reasonable on it's surface, however for anyone that is tried to start a business, or sell anything, there is a big gap here.

The gap between creating something useful (an app) and the ability to sell or market it is HUGE. That gap is the difference between useful or not.

So I agree, lots of "useless" stuff will be made because the drive to close that GAP (which looks small) won't be done because there is no need for it.