I was obviously a more skilled gamer when I was younger, cause I could beat CV3 without much trouble back then. Nowadays I get about halfway through before things start to get frustratingly difficult. Same thing with many of the Mega Man games. I guess it's a combination of age and less time to practice my skillz!
Games these days aren't nearly as punishing, they're just kinda... long.
Number 1 reason for not finishing current generation games is utter boredom, unfortunately.