You do quite often.
Last season Madrid were the best team in Spain. That's true. Barca and Atleti were far behind for various reasons.
But they were not even close the top4 in europe, even despite managing to eliminate them in knockout ties.
In 2021 they reached CL semis, yet they were not even close to the top4 that season either.
Cups are unreflective of best teams more times than they are. Abundant historical examples of that.
The best team in Europe every season is not determined by who wins CL, but by a number of factors such as how dominant the teams are in their domestic and european games, what football do they play, etc
Until the real Super League comes (which will be a league, and not a cup), we won't have an indisputable metric which team is the best in Europe every season
To be honest I don't exactly agree despite really wanting to agree with you and thinking you're right on this topic generally. I would say CL should be taken into account with other factors but there are proven examples of dominant teams domestically consistently being poor against the best in Europe (just look at Barca).
The problem is, as much as our xG brains don't want it to be true, and want there to be justice in football where the team who wins in the midfield, defense, attack phases, and outplays the opponent, wins the game, unfortunately, the conversion of chances and mentality of a team plays very hard into how good they are and if they are likely to win high pressure games.
xG can be seen as a reflector of 'who played the better game' in general. But when you have very capable, talented attackers with top mental skills like Vini and Benzema you are going to win most games creating the same amount or even a little less than your opponent, that is the idea that Madrid have won most games based on.
So in a game where Madrid don't play the best game but create a few chances anyway they always have a chance because of that amazing finishing talent. The only way to definitively beat them is to deny those two chances completely, easier said than done, but current Barca have done it several times, maybe why we make it look so easy.
Yesterday is a perfect example - with Rodrygo instead of those two, but Chelsea and Madrid create roughly the same across the whole game yet Madrid ended 2-0 despite it being a totally wrong reflection of the game - they backed their finishers to come through and obviously, the story of the season for Chelsea is how theirs don't. Finishing talent and mentality of a team, and their goalkeeper, have to come into play when analysing how good a team is based on xG.
You can say they weren't tactically better - absolutely - but just had the far better individuals in attack. Maybe in a Super League that would improve because opposition teams can get used to playing them a lot more, drop their fear of them and tactically adapt with more info.