However, Real Madrid had three goals disallowed in that match. If two of those goals hadn't been narrowly offside, the match would have ended with a four-goal victory for Real Madrid. We wouldn't be making these comments now. So, even though they weren't playing badly, winning matches by narrow margins shows us that they have some problems. Disallowed goals are irrelevant. So, you're essentially right.
Having multiple disallowed goals shows that they had a good performance and were probably unlucky, they were not playing badly and the narrow win is not because they did not perform well, or that they had an issue, they will likely do even better there after. Except for the coach who is trying to get along properly with the team I do not think Madrid is having any issues even in they game. So it is just a regular experience with the game just like every other team.
I agree with your opinion. If the goal hadn't been disallowed, Real Madrid had scored many goals in that match, so the disallowed goal was an unintentional error. Real Madrid would clearly be more careful in capitalizing on their chances so their goal wouldn't be wasted.
I think Real Madrid still has good attacking ability. Just because of one mistake, we can't speculate about their shortcomings unless Real Madrid truly shows a decline with the defeats they've suffered.