@John-Long,
The number to watch is not on the result (MT/s) but on what makes it happen is that prefetch number. This is the number that continues to double between the generations that you mentioned. That number is about how much data can be accessible at any one point in time. This time that number is about bits, and bits doubling allowing more binary data in in each generation. the 2n is 2^2 = 4 bits = 4 , etc. by the DDR5 it's 2^16 = 16 bits = 65, 535. Each successive generation has been able to process more data at the faster speeds you've mentioned. An analogy: how many people you can carry, on a speed-bike you can carry 1 or 2 people really fast, but it's still 1 or 2 people. But if I drive a school bus that has more seats but also is faster than the speed bike...how many more people get to the destination faster? Those bits then are about capacity at a given speed.
This is the tricky part. If you have a mobo that you can mix and match ram, which most don't but if you do...it will only go as fast as the slowest speed ram you have...which means you can make faster RAM go slower; but you cannot make slower RAM faster.