I'd guess that it hasn't become an issue with any of their clients. If any big client had been impacted once, they would have sped up moving. If a big client had been impacted twice, they would have moved already.

That's fair, and I agree (hope?) if it was customer impacting there would be a miraculous allocation of scarce resources to move platforms. But in my world I'd get asked "why are you still screwing around with a vendor that clearly sucks" even if it was for a non-prod playpen of no consequence. YMMV.