Probably because the Taurus was the #1 best selling car for 5 or 6 years straight, which means few people would agree with you. I've never heard anyone who owned one complain about the quality.
Really? You must not know too many people who have owned them. I own a 1996 I unfortunately purchased brand new and it has been the biggest pile of crap I ever owned next to the Hyundai I once owned. The motor is currently blown. Before that the rack and pinion let go while driving it. The transmission (a notorious weak spot in the Taurus) quit once. I've towed back friends Tauruses with blown transmissions more than once. Every person I know who owns a Taurus has had numerous problems.
The reason it was the Number 1 seller is due to fleet sales.
Period.
This car that was introduced in 1984 and has been one of the best selling cars every year since....that 18 years running...
...and YET you asked why it wasn't listed as one of the 10 worst cars of all time.
LOL.