I don't think this "my fault" / their fault is a useful way of thinking for enterprise decisions. For my part, I was and am in charge of cloud (and on-prem) purchasing decisions and I don't like to consider these things binary. Counterparty risk is just an additional cost to consider.
We use Alibaba Cloud, GCP, and most of all AWS. About December last year, Alibaba Cloud had a full zone outage as their datacenter provider had complete air-conditioning failure. One of the first things to go were the switches plugged into Express Connect (their feature to allow you to have direct links to their cloud through your network provider) and we had backup access set. We didn't get all of our stuff shut down but it helped.
But developing and maintaining backup access costs something. When we egress from S3 to our on-prem cluster, that's a cost. Vendor continuity and substitutability is just a cost like that. It's up to the guy managing this to model each of these risks and no enterprise vendor will sign an unlimited liability contract so you're going to have to land somewhere reasonable here. I always make sure to have exit clauses for us, and I try to ensure vendor exit clauses are what I'm comfortable with and appropriately priced.
Ultimately, you'll just have to read what you sign and have good counsel. But that's just what's worked for me. If you find the blacklist model more successful, more power to you.