AWS literally paid for developers for the redis project, including the salary of core members. It's not like they didn't contribute back to the community.
They pay for a lot more open source work than that as well, but they also don't get to make any special claims for doing that. None of it is charity - it is simply in the collective interest of a lot of tech companies to commoditize and share the costs of infrastructure software. Even shaming freeloaders is uncalled for and against the ethos of OSS, which is sort of implied in making your statement.