So let's talk Mach 1 history. Seeing a lot of hate out there. In 1969, a Mach 1 was essentially a GT. They killed off GT after 1969, because they sold 14x more Mach 1 than GT. Yes, 14x more!
Engine options were not much different from a non Mach 1, and even the most stout 428 Cobra Jet shared a horsepower number with modern 4 cylinders (and entered the scene in a previous vehicle). They also had stickers and spoilers (lots of people whining thats all the new one is) Car also had some mild suspension improvements.
Another note, less than a 1/3 of them had a Shaker.
So 2003 rolls around with the Terminator. People want a gap car. The Mach 1 enters. What is it? A GT with a 01 Cobra motor and some small asthetic tweaks. Or if you prefer, an 01 Cobra with a solid axle. Regardless, nothing new. Just a new package with some styling tweaks. (albeit a .25 compression bump)
Now, the 2021 Mach 1 is here. It has more unique parts on it than any previous Mach 1. More tech. More handling upgrades. Subtle appearance modifications. Engine upgrades from a previous specialty model. Improved transmission options. Even a unique torque converter and extra cooling for the auto. Etc.
So, basically, the new one is EXACTLY what the Mach 1 has always been and more. A "parts bin" car with some unique touches. And guess what, the last variants are still doing just fine
Everyone has their own opinions, and that's fine. Just don't forget to look at the history.