For my part it goes along the lines of 3 things:
1. Does it make enough money to justify it, because while yes Amazon has money to spare if the show is consistently losing money that means it is either massively wasting money or not getting near enough viewership to justify spending the money on it vs other shows.
2. How is the reception of the show? This is a much harder to measure statistic as there are like you said a variety of measurements for it, be it the actual viewership (which we can really only speculate about), the amount of secondary product it drives consumers to buy/view (a much worse stat for amazon because unless purchased/watched on their website they aren't getting money for games/toys/etc), and the general buzz/talk about the show (be it online or in person). The last one is also fairly hard to measure as you can't get a number for person to person talk/watercooler talk about the show, but the online buzz for the show was IIRC 10% of HotD, a direct competitor for the fantasy genre and what Bozo himself said he wanted to create/beat.
3. Finally pride/quality of the art created. This one is another that is hard to properly measure as some shows/movies people love and others people hate. It in part is related to the other two as well, as money/talk can certainly point to quality, though it isn't always the case. Sometimes shows/movies that are masterpieces never make the money/name they deserve, but at least people can respect the work still. For me a good example of this (that also happens to be adaptation) is Dredd. The movie was fantastically made, enjoyable throughout, and captured the essence of the source. Yet the movie lost money, and while it has an okay cult following, it didn't drive press/talk. Rings of Power other than the CGI doesn't really drive people to love it, it doesn't have that "It" factor to make something about it immortal/have a cult following. Even the people I know that enjoyed it didn't have a thing about it that they loved, they just enjoyed it. As soon as another pretty show comes around it will be largely forgotten.
So TLDR with the show having an amazing/immensely well known source, the largest budget for a show ever, and one of the easiest/best value subscription/methods of access, what we got was not a rousing or even good success, heck personally I see if as a massive failure. However even if I view it subjectively I wouldn't be happy with the results if I was amazon, as the show was given a diamond spoon and produced results you can get from much cheaper shows like Reacher.