The third-generation Cougar was introduced in 1974 and marked a departure from previous models. The car wasn’t based on the Mustang, instead moving to a heavier chassis. This meant Cougars were more personal luxury cruisers than muscle cars even though Mercury tried to present them as such. Even with the optional 460 V8 with 220 HP, acceleration times were disappointing as a result (via Hemmings).
Mercury moved the Cougar to the personal luxury segment and away from its muscle car roots. Cougars were cars for middle-aged Mercury buyers who wanted something more sporty than a Thunderbird but with the same level of comfort.