There is, as shown in the other posts, lots of reasons for the decline of men 8 and men 9 skiers performances. One is the fact that we have less skiers in the these divisions. Another is lower boat speeds are not always beneficial.. The top skiers in these divisions can still ski into 35 and 38 off at 30 and 32 MPH, and some would say they could ski the same or better at higher speeds. I think you will find the divisions are very competitive when you have so few skiers- I'm impressed with those at the top. No doubt it is harder for these skiers to stay in shape, keep improving and break bad habits than when they were younger. Personally, mental reaction affects me the most. Because of that 30 MPH ended up being a benefit even though I initially found it harder and didn't like it. I suspect there are bigger/heavier skiers who found it extremely difficult to adjust and ski at that speed.
If you compare, current performances in Men's 8 and Men's 9 to 5 or 10 years ago, I think you will see that we now have more skiers with high scores.
It would be interesting to hear your thoughts after you make your comeback. I wish you well and assure you the older divisions need skiers.