Way way back, when Amazon got bigger than just books, my motivation for using them was a) very good selection (in one order, I can order bagel chips, wiper blades and a router?) and b) price. Implicit in this was authenticity and good customer service -- for me, if the product isn't the real thing, or the company is a nightmare to deal with, it's a non-starter.
Well now here we are. Fake reviews, counterfeit products, most things (IME) are actually FBA or just outright 3rd party sellers (not automatically bad, but more opportunities for problems), their prices aren't competitive anymore...
So, they've still got a lot of selection, although it's really more like shopping at a bazaar, since really their website is almost nothing more than Ebay in some sense, and I will say their customer service has almost w/o exception been stellar. But that's not enough anymore.
We'll see. Nothing lasts forever. Either Amazon will get the wakeup call and tighten its ship, or it will become the next Ebay/Myspace/Craigslist (I'm deliberately just throwing the kitchen sink here).
One last footnote -- just within the last week or so, 2 Amazon tech products that I've praised -- the Ring Doorbell and the Eero router(s) -- had firmware problems. Ring bricked itself (firmware update gone wrong) and had to be RMA'ed (they did it w/o any problem, and this was almost 2 years after purchase). The Eeros went into a cycle of resets and couldn't update their firmware.