Not sure there’s a right answer here other than what works for the individual — as what motivates us is different.
For what it’s worth as another individual - I use the 4DP metrics as a goal within a wider goal of being able to do more when I’m MTB’ing.
But I can’t metrically measure MTB’ing in the same way I can metrically measure 4DP. When MTB’ing there’s even more variables involved for me so I use 4DP as a ‘mechanism’.
Arguably either (MTB efforts stats or 4DP) of these are just ‘measures of my own making’ and subject to all the vagaries of a human body having a good/bad/medium day etc etc. just what I choose to measure myself by.
As far as actual numbers goes I’m ok personally with me setting a number but i do find these numbers are much much smaller.
So last year I aimed for a 2% increase (240 to 245) in 20 min power. It actuallly went down after a few plans (by the measure of a few 4DP’s). Hey ho. I was still ‘fitter and healthier in body and mind’ for trying.
This year I did the same, this time it is going up a few percent. But that’s it. 1-2% a year down (and up) barring as some have said - people who are new to the sport, detrained, maybe major change in life allowing more focus/time to train or such like.
As long as there’s some fun in there …