Size does matter. Those that say is doesn't are clearly in denial or just plain fibbing.
Some of us guys understand that we have to play the hand we've been dealt. As you can see from my avatar, I'm 5" at best, probably closer to 4 1/2". BUT, my goal remains to please my partner, WHATEVER that takes. If it means oral I'm there, if it means helping her masturbate to completion I'm there as well. I am secure in my sexuality and know my limitations.
I used to be larger about 6 1/2", but years of non-use and age has caused my dick to atrophy. I can no longer hit spots I used to. "It's not the size of the boat but the motion of the ocean"--- BULL. I don't care how good a guy can move if he can't get in deep enough.
Add to that the mental part of sex, most men do not get excited seeing small boobs, or a huge posterior of tree-trunk thighs. Be real guys, to women a beer belly isn't pleasing nor is a poorly trimmed beard or a small dick. We all have mental images of what is and is not appealing, ergo exciting.
But of course too big is just as bad as soon too small, My wife said too big hurts as the guy bottoms out. Too fat hurts as well and remember the vagina looses elastically as a woman ages.
SIZE MATTERS - IT ALWAYS HAS - IT ALWAYS WILL.