Town Car is no longer because sales fell off! Sales fell off because the consumer change buying. In no small part to SUVs and Crossovers.
Other domestic car manufacturers pulled out of full sized car market long before Ford did with the Panther platform. (Crown Victoria/Grand Marquis & Town Car)
The Panther platform WAS successful. Beyond anything that Ford had expected. Ford was going to end the Panther platform several times earlier. The first time was in the 1980s. However sales were still good even though that consumer was shrinking. Given the consumer base was getting smaller the competition left leaving the market for Ford to sell. The entire platform was changed to reduce costs over the years. In the beginning the platform could handle larger trailer. That was down played as CAFE requirements were bearing down. The modular engine used in later years was the cheapest and lower power version. Options got lumped into packages to reduce manufacturing costs. In the end a lot of cosmetic things were done, but under all of that, the car was rather cheap to build. This was done to sustain sales as long as it did.
The Town Car not being made today isn't a failure. Many models are no longer being made. The Town Car and the Panther platform were a big success! It was built for 30 years. Not a common thing in the ever-changing car market. And car companies HAVE to change because the consumer changes. Some time on a dime. The car companies that do not change or change away from the consumer go the way of a De Soto or Packard.
And the best engineered car isn't made by any mass production car companies. It is unaffordable because the mass public isn't going to pay for that kind of engineering, It takes money and that money comes from the consumer. In addition to that, it costs money to comply with all of the regulations. Money that could be spent on other areas of the vehicle.