What he really got at was not about modding it, its about not making excuses for your lack of ability. Modding for fun is different.
To put it in different words
There are many that complain and say "my sled is not like yours it wont do that" or this sled just wont do that. The truth 90% of the time is you can't do it but the right rider can, so work on yourself first, extinguish every possibility that it may be you and not the sled and at that point mod the sled.
Being in shape helps you get to that point, instead of getting tired and avoiding the hard stuff.
I see it a lot and have got on that guys "old or stock" sled to prove its not the sleds fault. When I was learning and moving up I used to have another guy that is one of the best riders around, do just that. So when I couldn't do it or thought I couldn't, I would tell him my sled wont do it (just to get a response) and he would say something sarcastic or BS, so then I would challenge him with a bet or say prove it, or your full of it until he got pissed. Usually he would jump on my sled and half the time pull it off. (which is what I wanted) at that point it took away my excuse in my own mind and I knew it could be done and then within a few rides I was doing it at some level.
Most guys will get butt hurt and quit riding with ppl like that. I know, most of my chit talkin riding buddy's are no longer riding buddy's because they can't handle someone eliminating there excuses.
But since MM said "everyone" I just couldn't help but throw him some chit.
IMO being in shape and mods is not the issue for most, its there thinking. The first 80% or more is all about the thinking, then after your thinking is right and only after, its about your skill level and the shape your in to maintain skill level. But like he is doing, Being in shape increases your thinking because you are more confident, which in effect the thought plays a larger role than anything.
If you drop your pride, eat your words and take responsibility you learn fast.