You're right, nothing stops them from becoming shitty. However, unlike public companies, a private company isn't encouraged to prioritize short term profit over long term profit. Doing something blatantly stupid to bolster your short term profit only makes sense for your shareholders or if you want to extract as much money before jumping ship - neither should happen anytime soon with steam.

Your pain points from the developer side all seems valid, and they should absolutely be improved. They probably treat unknown indie devs like dirt because for every good game they get thousands of submissions with blatant lies in them. E.g. your typical asset flips. Of course, that's no excuse, but at least I can kinda get where that could be coming from. Have you experienced the old system? I simply cannot tell whether they have truly become worse for indie devs or just traded some problems for others.

Regarding the sales, I have mixed feelings. Sales were a lot more exciting, that's just true. However, because of flash sales, I mostly never bought anything but those, at least until the very end of the sale. While it is boring in comparison, as a consumer, I also quite enjoy the ability to only check the sale once, get what I want, and be done with it. Seems way more convenient.