Balancing data set: I've been in many Waymo in Los Angeles and never had them do anything like this. Since you mentioned going to the airport presumably this was in Phoenix or San Antonio? Seems like the traffic on those places would be sub-LA level of difficult to navigate.
San Jose. The 15mph incident was mid-day, broad daylight, hardly any traffic at all. Airport incident was at 3 AM at SJC.
In LA they make very subtle traffic infractions. For example, turning right onto the left lane of a two-lane road. But a third of human drivers probably don't know that it's not allowed and another third intentionally violate it.
The ones in LA just get stuck behind things because LA loves its park anywhere you want anarchy.
But also the Waymos use alleys, driveways, and private parking lots that they're really not supposed to.
Always a bit embarrassing when the Waymo decides to use a space that's not meant for public use for pickup/dropoffs. One time, mine waited for me in/blocking a fast food drive-thru lane.