AWS has many cool toys and I use a subset of them every day. However, there's no way in hell I'd entertain the idea of going in fully for everything we do. Not only are there a bunch of inadequate services, they can also be nasty to debug and cause more problems than they're worth.
It sounds like you may have an inexperienced guy getting overly enthusiastic about what he could achieve instead of focusing on what's required (I don't mean to insult him, it just sounds like he may not know enough about infrastructure to be making these decisions properly). Being provider agnostic (at least as much as you can be) is currently a way I see a lot of companies starting to leverage the great tools that cloud providers have, but being able to be free enough to chop and change as the companies needs evolve.
Maybe point him towards things like Terraform and get him looking at what Google cloud and Azure can do as well as AWS?