That's one way of looking at it. Parenting had changed me profoundly for the better, and even though I made horrible mistakes as a parent (as most people do I guess) I've also managed to significantly improve many shitty aspects of my personality.
I think in parenting most of all you learn to give, without hesitation, without thinking too much, you just give to you kids whatever they demand, out of your unconditional love for them.
Besides, if you wish to become a happier person, kids are such an amazing source of joy and hope! Oftentimes kids can see things much more clearly than adults, they have their own kind of intelligence and reasoning and we adults have much to learn from them.
There are many more "selfish" reasons to have kids. If you do it right and develop affective relationships with them as they grow up, they'll take good care of you when you grow old and frail, and your grand kids will bring you even more joy and entertainment! I don't think it's much fun to be old and alone...