Having taken a few robot vacuums apart, you are spot on. It’s very noticeable. The roombas are the better engineered ones. The worst one was a Shark. It was toy-like in its construction, the wiring was messy, it was simply unpleasant. Also unpleasant but a step above were the neatos. We still have an xv21 that runs daily. Its lidar tech was amazing at the time. Early xiomi roborocks were blatant copying both the lidar and motherboard.
They were a joy to repair: every part was made to be easily replaced, not "engineered" with glue, or pegs that break.
Could tell it was tech started at the MIT AI Labs.