I honestly don't agree that the MC is drifting through life. He's a bit of a wimp, sure, but he knows what he wants and lives the life he enjoys. He seems to like his job, he's got a cat, so he isn't financially struggling and clearly capable of taking care of something else other than himself, he just has no interest in starting a family or having a super active social life, which is fine, isn't it?
Although it does show the interesting conflict between old and new, where his father clings to the idea that getting married and having a family is the next logical step at his son's age and anything else is just faffing about, while the MC is satisfied with what he has.