I think it'd be more accurate to say "Even /fairly large/ web companies can now be built [et cetera]". Good luck putting Google on AWS. Or (relevant to the name of this website) AWS.
I think now you could even build a fledgling Google on AWS. Once you start getting real traction then you may outgrow it but there's really no point in even talking about those steps until you have a few million users beating down your door.