There are only so many places you can order stuff on-line locally, to save on non-food products more expensive or downright unavailable locally. Interfacing with individual vendor and their bespoke system for each purchase gets cognitively exhausting quickly - a major reason why people prefer those large marketplaces. And then, it's not just Amazon. Adopting such policies is becoming a trend parallel to centralization. Amazon alone may not be "super critical piece of living a fulfilling life", but getting banned by it and a few more large companies (Google, in particular), and you may lose some critical things (at least critical in immediate term).

> Interfacing with individual vendor and their bespoke system for each purchase gets cognitively exhausting quickly

If using a web shop is cognitively exhausting to you, there likely are bigger problems underneath.

A single one, no. Two dozen different ones - I can do it, but it gets so annoying that I'll happily pay premium to buy the same things on a single site.