I wonder how much of this was due to the lack of transport opposed to accommodation. I really enjoyed the (limited amount) of Bilbao I saw, and plan to re-visit at some point.
My experience of getting to Bilbao was pretty straightforward, I booked direct return flights back in April, (Gatwick to Bilbao), no delays and both flights were ahead of schedule, and getting through passport control either end was fine. I was out of Bilbao airport within 5-10 mins of landing (first from the flight), and I headed to the Uber pick-up point.
It took over 30 mins for an Uber to arrive after booking (no others arrived for other before mine), he'd driven straight from the city centre after dropping someone else off. This was Tuesday evening, a full flight from Gatwick, followed shortly after by a full flight from Manchester. Then getting from Indautxu area back to our Airbnb Santurtzi was about a 30 minute wait too. Others in the group had the same waiting time issues with Ubers too.
On match day we got the train from Santurzi to the fan-zone, and then walked to the ground. After the game, we had a couple of beers in the Indautxu area again, and we decided that we'd get the Metro back to the Airbnb as we didn't want to risk the long waits. Speaking to another friend who was there and staying out of town, they ended up having to get to the airport to get a taxi and didn't get back until about 7am.
The transport infrastructure and volume of hotels in the city probably wasn't suited to having 2 clubs the size of Tottenham and Utd, and was surprised that there weren't more Uber/Taxi drivers, or more Airbnb's listed in the city centre.