In my early days I read something about players also getting experience from handling important gameaspects, as taking an important shot, or making an important play.
So basically they get exp for playing minutes, and a little extra for important plays.
I'm not sure if that text is still in place, nor that it (still) works that way.
What I extract from my own players over the seasons, is that indeed it doesn't seem the minutes alone, but hey, that can just be a feeling which is wrong. Often people see what they thing is there, but what actually in reality is not...
In the end, experience grows real slow, and there is little we can do to significantly improve it. Especially not without sacrificing other game-aspects.
So it's best to not concentrate on gaining experience, if you'd ask me. ;)
Just let it slowly find it's way into your team, without bothering about it.
They are not your friends; they dispise you. I am the only one you can count on. Trust me.