How can tech startups succeed with 0 barrier to entry?

I'm not from the "startup space," but have been learning about business/startups. In this case, I'm specifically referencing tech startups which have some idea (a dating app for dogs, let's say) and then code/develop to build that product and sell it. (not referencing a more technical solution, like building some very proprietary cryptography software that requires a lot of experience to make)

Right now, computer science is among the most popular majors in university, and also many people without computer science majors can very easily learn how to code, at least enough to build some products. With ChatGPT, this has only increased, so much so that MVPs can literally be built in like months if you know what you're doing.

I'm not trying to question anything, but as a newcomer, I'm trying to learn about it. What I'm trying to understand is how can startups be profitable/successful at all when the product itself has no intrinsic value. There are literally tens of thousands of people who can probably re-create your app/idea, so then the fact that you've created such an app has no meaning, except for the fact that you happen to have come up with the idea. And, also, because the barrier to entry is so low, many of the actually viable ideas have come to fruition, so the marginal value-add of whatever you are doing will, on average, be less than the marginal value-add of what people did 15 years ago, when software was fresh, products used software in new ways, and products were hard to make.

If you have some tech/software idea and build it, how can the startup be worth anything?