That doesn't make a whole lot of sense. Plenty of guys stay away from marriage and long term relationships because it's fucking torture for them, not because they aren't capable of doing it.
I agree with liesnillusions, 9 times out of 10 long term relationships are pointless time-sinks and get in the way of ambitions and dreams. Most girls offer little to nothing outside of sex, they suck at stimulating conversation and take every joke seriously. You end up spending so much time and energy trying to 'make it up to her' when she thinks you fucked up when in reality she is emotionally needy and needs to latch on to a stronger person to get through life.
Start taking a tally of how many times your girl expresses that you need to change something to make her happy and vice versa- the girl always wants you to change exponentially more than you want her to. They are vain creatures who train men like dogs using sex as a treat.
It's not like I aim low either, I would never even think of being in a relationship with a girl I would classify as 'stupid' or a whore. I've been in a relationship with a psychology major for almost 2 years now, and I know it's the closest I'm going to get so I'm just sticking with it. I fantasize very often about being free of it, I certainly wouldn't say that someone who chooses to stay away from these relationships has a 'shitty personality', there's a big difference between avoiding relationships and being unable to maintain them.