If AWS or WPEngine release their sources, then they are upholding their end of the bargain. Why shouldn't they make money, if they can?
If they are not releasing their sources, because of inappropriate licences, then that's what licenses like AGPL are there for.
I've got much less of a problem with AWS making money than I do with Canonical replacing GPL code with knock offs designed to cut the community out of code sharing.
It’s not AGPL though, and AGPL would have solved the underlying problem. GPL existed to force companies to release changes so “I can have it also”; and that’s a political view, the whole “free as in freedom”. Cloud wasn’t accounted for in this pre-centralised internet. 2001 (B2), is long before AGPLv3, but if you have the same ideology, that’s what you want. You built a thing using GPL based code, I want it also.
Freedom is never a given, it must be continually fought for or lost.