By default if you buy something in a store, add 5% to the value by improving it and want to sell it on eBay, they'll charge sales tax on the full sale price even though you already paid sales tax on 95% of that. To avoid the double taxation you have to file paperwork, which most people don't know how to do, and pay filing fees, which eat into your already-meager profits.
If you want to sell things over the internet yourself, or accept digital payments in person, how do you avoid paying a fraction of the sale price that may exceed your margin to some payment intermediary that may capriciously choose to cut you off at any time with no recourse?
If you want to incorporate, your annual fee is the same one paid by Apple, but e.g. $500 is a lot more to you than it is to them.
Keep adding things like that up and individual-scale operations are no longer viable without charging thick margins and thereby having only the affluent as customers, which is what happened.
You're ignoring the middle ground, because that's the thing that was destroyed. The expert potter is still in business selling bespoke products to millionaires.
It's the one who might have done it for 15% more than the mass produced product who is gone, because we added on top of that so much bureaucratic overhead that the final price ends up being 100%+ more instead of 15% more and that exceeds what ordinary customers are willing to pay.
Why would you buy a product for 15% more, unless there's a compelling reason to do so? The mass produced ceramics are high quality, durable, come in a variety of shapes, colors, sizes, etc. People buy hand-made ceramics for the aesthetics, and to have something that's more unique.
I think you greatly underestimate how much cheaper mass produced goods are than artisan made goods. Op's choice of ceramics is really good. Machines can produce thousands of plates in the amount of time it takes an artisan potter to make dozens. The potter's source of clay may be limited, or they may have to pay a lot more because they buy in smaller quantities. They have to pay more for transportation for the same reason. They have to pay more for distribution for the same reason.
Bureaucratic overhead may play a part in this, but overall it's a small one that gets lost in the scale of mass production.
which is what makes it cheap and available.
If you ran your own farm stand, the goods you produce would be some 2-5x more expensive than a factory farm could've sold for.
The modern wealth is predicated on such specialization and scaling. It's why artisanal products are so expensive.