Those reasons have nothing to do with Uber being unable to charge more for the rides than the cost to provide, which is not true and a widely held misconception.
An investor should care about "can they make money selling rides". That business unit can always be broken off from orthogonal ventures.
So instead the question becomes how long they can keep exploiting workers like this. AB5 suggests that the answer is not "forever".
Amazon breaking even is very different from Uber lighting cash on fire to keep the lights on. Amazon was working towards something - becoming the best online shopping place possible (and building the logistical infrastructure to make that happen, allowing them to offer better services such as guaranteed fast shipping). Uber is just continually rearranging the chairs hoping to keep it going as long as they can.
There is nothing about Uber that scales without losing more money. If there were, they would have figured out how to make money by now. It's not like they haven't had enough time and money.
Unless you think that Uber is somehow going to pull a high margin non related business out some type of way, it’s really a horrible comparison.
Uber was certainly technologically innovative a decade ago. But a lot of the mobile and geo stuff is now off-the-shelf or as-a-service tech. Now that they're not subsidizing rides, even in this discussion we see people feeling the pinch. Uber's going to have to extract a lot of profit to reward investors and pursue growth. I think they're becoming vulnerable to low-cost competitors who just want to get by. E.g., driver co-ops and local specialty companies grabbing market niches.