Interestingly, I actually still have only had great experiences with Amazon customer service. I have a feeling that is entirely due to how much my family continues to spend with them, though. It is pretty well known that their customer service response to things varies with how much your spend.
The customer service is a margins game, and you are correct that they ratio spend to returns to track those margins per account.
The service degradation is in terms of search no longer being useful, promoted/ad brands everywhere, popup 'businesses' with co-mingled inventory, fake reviews, just general lack of trust earning. Amazon used to be THE place to get the cheapest option too, but that is rarely the case these days.
