My job is to deal with factory warranties and extended "warranties" which are really service policies.
There are some good aftermarket warranties. Some.
But it's like the stock market. Many go out of business daily, leaving you stuck with thousands of dollars in repair bills.
They can pay your dealer with a credit card, you can leave the dealership, the extended warranty can go out of business, the bank the credit card is drawn on will charge it back to the dealer, and guess who the dealer goes after?
You.