If the length of training is going to bother you, MD/PhD probably isn't for you.
Unfortunately, both clinical medicine and research are the kinds of things you can only really learn by doing; there aren't many shortcuts.
On the bright side, only the first couple of years are like school. After that, you're always doing it; either in the lab or in the hospital (sort of like as an apprentice). And that carries forward for the residency part, too; you're more like a journeyman physician and scientist, if that's what you want, since many MD/PhDs do both clinical and laboratory work during residency. And then after that, you get to be a master of both, if you want to arrange your life that way.
But no kidding; it's a long road to become either a physician or a scientist. And becoming both can take a ridiculous amount of time. If you can't take a long view of it, then it's probably not the right path for you. And there's nothing wrong with that, as long as you recognize it about yourself.