I took cruise at least a dozen times, back when they were giving free rides from downtown SF late at night, originally advertised as a promotion for restaurant and hospitality workers going home. (I was just hacking late into the night ;) I lived on the other side of town, so it was about a 6 mile trip.
I can't speak to their technology, but generally speaking Cruise seemed too cautious, both in the aggressiveness of the driving, and in how quickly the company capitulated. I've taken Waymo a few times and what stands out to me is how aggressive Waymo cars are. As a passenger this aggressiveness makes them feel more sophisticated, not to mention faster, but the cars also spook pedestrians to a greater extent as they nose their way into traffic or through turns. Nonetheless, Waymo has been more adept at moving past bad publicity than Cruise, including in the face of accidents.
Above and beyond whatever technological shortcomings there may have been[1], I think there was a management and business development mismatch between GM and Cruise. Cruise manifestly worked well enough. With better management--more honest, but also more aggressive--it could have been a contender; heck, it was (is?) the only proven competitor to Waymo for autonomous public taxi service, at least in the U.S.
[1] In 3 Waymo trips remote intervention was required once, which is a comparable ratio to my Cruise trips.