I agree it is not Steem but I don't agree that means the entire subjective rewarding pool concept has been transformed into all content and nothing but content. That never happened.

What if a bunch of big whales buy into Hive and literally do nothing but massively upvote their own pet projects?

If they own it, at least in a dominant way, they can do as they like. If there are other stakeholders who don't agree, they can downvote. I've always maintained that downvoting is essential to establishing a consensus on how the reward pool is to be directed, otherwise it all a shitshow of stakeholders, big and small, voting their own pet projects (including recurrent "content" posts, which is a form of pet project, after all), and which often doesn't benefit the broader platform very much.