I watch a shitton of golf videos, from club fitters like Champion (Ian), 2nd swing and a ton of others with Trackman facilities. They've all done 20 yr v 10yr v new equipment testing, diff stiffness testing, graphite vs steel shafts, same lofts different iron head types, etc. You will be amazed how little difference there has been in the last 10 years for drivers and 20 years for irons (except for hollow bodied). You will see VERY little difference between each generation. For drivers from 10 years older to now, it may be 1 or 2mph ball speed improvement, slight improvement on dispersions, not much improvement on distances, some improvement on spin (lower or more spin, depending on what is needed).
For irons, it's almost a zero improvement as long as your are comparing between club types. Blades are gonna blade. Cavity backs are gonna cavity back. Hollow bodied are "newer" but at the end of the day, it really comes down to loft and spin.
I gamed Srixon Z565/765 combo irons. I upgraded to ZX5/ZX7 irons. They are absolutely the same. I used to game a Mavrik Max, but 20gram weight moved up so less spin. I bought a Paradym X and saw no difference. I used the same shaft in both. I went back to the Mavrik because the elongated head shape offered enough forgiveness and the 20 gram weight moved up to the heel lowered my spin which I wanted.
My scratch buddy gamed AP2s. He did a fitting and got T150. He's struggling with the T150s. He lost his stock baby fade and has a harder time shaping his shots. Played 2 rounds with him the first 2 times he took out the clubs. Both were the worst rounds he's played in years. Maybe it's between the ears. Maybe he should've been fitted in the T100s. Who knows.