@moorebrother1 I agree, the primary reason to play magic should be for fun. If you are not having fun, you really should step back and re-evaluate.
That said, I don't think the approach of "asking your opponent to tell you what you did wrong" is very effective. Your opponent doesn't have perfect knowledge of every decision you made. They don't know what your other options were. They may not know how to pilot your deck. Or they may not be willing to tell you because they don't want you to beat yourself up about it after a loss.
This is especially true when it comes to Xerox, in which many of the decisions are made in hidden zones (hand, library, etc), and many games go long. Do you remember every scry decision over the course of a game? Every spell you could have countered, but chose not too, and which countermagic you could have used? Because your opponent is not privy to this information.
For the record, I didn't want to make this post about you. I know you were the OP, but the headline seemed to be asking for a general account, and many people were weighing in with their own perspectives and approaches. If you meant this post as a way to make up your mind about the Vintage format, that's fine, but I don't really have anything to contribute.
@IamActuallyLvL1 Most Vintage is not really played at a GP+ level. Joe Brennan mentioned that he has a 80% win percentage in his events. Joe is a great player, but such a win rate should be unattainable over the long run in a more competitive setting. As you said, pros tend to plateau at 65%.