I don't see this as a "modern" vs "back in the day" thing.

The real reason many software orgs nowadays don't have QA is for the simple reason that it's slow. Everything in the consumer tech space is about rapid growth, and moving as fast as possible. Nobody cares very much that the software has bugs, what matters is whether it has users.

But outside of consumer tech, QA is a lot more common, since it matters a lot more that the software's logic is correct. (Speaking personally - I used to work for a genetics lab, and we had QA.) There are just different economic incentives involved.