And yet somehow the shittiest buggiest software ends up being the most popular.

Look through the list of top apps in mobile app stores, most used desktop apps, websites, SaaS, and all other popular/profitable software in general and tell me where you see users rewarding quality over features and speed of execution.

I don’t think this search will really reveal speed of execution and feature set rewarded over quality either.

You have it backwards. Excellent software becomes popular, and then becomes enshittified later once it already has users. Often there is a monopoly/network effect that allows them to degrade the quality of their software once they already have users, because the value in their offering becomes tied to how many people are using it, so even a technically superior newcomer won't be able to displace it (eg. Youtube is dogshit now but all of the content creators are there, and all of the viewers are there, so content creators won't create content for a better platform with no viewers and viewers won't visit a better platform with no content).

If your goal is to break into the market with software that is dogshit from day 1, you're just going to be ones of millions of people failing their get-rich-quick scheme.

Have you read the source for those products?

That is easy. Those top apps in mobile stores are constructed in part with compilers which are under great pressure from developers to generate good code as quickly as possible. There is often bloat at the level of the development environment or some critical library, but core developer tools are a big part of the software space and are made and sold with very different criteria from the most popular apps vended from walled gardens.