There's always someone making this claim when negative comments about AWS come up.

They almost always come from people that don't have experience running substantive infra at scale without AWS, so they can't make an informed comparison. The complexity of doing so, for a lot of infra, turns out to be lower than using AWS. Also, you end up with transferable skills and a deeper understanding of the foundational protocols and systems. And you save a lot of money, both because you don't have to pay to manage that complexity, and the systems themselves are cheaper.