And developers who are not full stack focused (more and more developers) - They make early bad architecture decisions and often don't consider downtime in the future of acceptable risk, therefore don't plan for it, therefore build applications that don't scale well.

It's fine to say in most instances you don't need more than one server that you can scale "physically" - but it's unfair to suggest you shouldn't consider the risks involved and the (sometimes very rapid) needs at future scale.