If you want to become a GM, have the time and motivation then you can become a GM.
That would be really nice if it were true!
Some people start young, have wealthy supportive parents, try for GM, but don't make it.
Look at the stats. I believe 2200 is already in the <1%
Well, anyway, I used to believe that too, so I suspect you won't believe me no matter what I say ;)
Try and don't make it? That implies somewhere along the way they lost the motivation otherwise they could still be trying. My guess would be that in most of those instances the person involved didn't really have the motivation neccesary in the first place. To imply that a mentally healthy human adult cannot reach GM level with proper motivation is a serious underestimation of the mind. Quote any statistics you want, it doesn't matter. The #1 reason for those statistics is that as far as value goes, chess is very low on the list for most people. If i told you that I would give you $10,000 for every point you increased your fide rating up until you attained GM status at which time I would give you $10,000,000 then you can be certain you would attain GM status.
No. Everyone has a limit. And, the ultimate limit isn't motivation or time - it is talent. Regardless of how dedicated you are, you have a ceiling.
I cannot dunk a basketball and am not sure I could even if I dedicated my life in training to do so. But even if I did, I couldn't touch the top of the backboard. Some people can, and they may have worked less at it than me.
It's the same in chess. You say we are underestimating the mind. I think you are underestimating chess.
You must be very talented then ogrady! Beware though that the hard work begins now, and a 1600 rating on chess.com is only about 1500 in real life.