So you would rather be incompetent than powerless? Choice of third party vendor on client facing services is still on you, so maybe you prefer your incompetence be more direct and tangible?

Even still, you should have policies in place to mitigate such eventualities, that way you can focus the incompetence into systematic issues instead. The larger the company, the less acceptable these failures become. Lessons learned is a better excuse for a shake and break startup than an established player that can pay to be secure.

At some point, the finger has to be pointed. Personally, I don't dread it pointing elsewhere. Just means I've done my due D and C.

If customers expected third party downtime to not affect their thing then you shouldn't have picked a third party provider or spent extra resources on not having a single point of failure? If they were happy with choosing the third party with knowledge of depending on said third party provider, then it was an accepted risk.