If just look at the engine in an M Car, you are missing the point. I can't recall the M division ever subscribing to any particular feature or spec as the defining characteristic. It has more to do with how everything works together to create the experience. Engines, suspension, brakes, etc all contribute to the experience. Everything has changed over the years. Engines, suspension designs, brakes, wheel designs, CF usage, etc. You could argue that M car should be homologated and hand built and the E9X M3 is a poseur car if you look at the roots of ///M which predated the E30 M3.
Like every other M3, I think the car will hold its value VERY well. Depending on how the DCT holds up, not sure if the E9X platform will command the same premium for 6MT cars like the E46 M3 does.
A clean E36 M3 still sells for over $10k nowadays despite being 14-18 years old so that should tell you something. The E36 is the most unreliable M3 to date as well.
2015 F34 328iX GT Glacier Silver
2011 E90 M3 Monte Carlo Blue
2004 E46 M3 Imola Red