If you have a newly built home, do you really think they're going to take your calls if you find an issue with the construction 6 months later?

Yes....because that's how the law works. Builders are on the hook long after construction is complete.

Furthermore, new construction has MULTIPLE waves of inspections throughout the build which makes detrimental corner cutting a lot harder. You obviously don't get that with prefabs of any kind.

It doesn't seem like you're very familiar with the industry. Builders get sued every day for problems they caused years ago. If they don't fix it, they get sued. It's part of the reason they're required to have insurance.

But, where I live at least there are a lot of very powerful builders who are extremely well connected to the government. I can't remember them ever facing consequences for shoddy building.

There's shitty builders everywhere (Lennar lol) who seem to operate for years with impunity but they're mostly doing full cookie cutter neighborhoods. Builders who do one-offs can be shitty, too, but have a portfolio and reputation for you to consider ahead of time. You just have to trust the images when you buy a house online