Let's not joke, Arsenal will never reach the final stage of the competition, the Champions League this year already knows who will go to the final and it certainly won't be Arsenal, with this I'm not saying that there is an agreement to make a particular team win, but there are several before Arsenal
The tournament hasn't even started, and you are so definitive about who will and who will not make it to the finals? I get it that Arsenal usually fail in this tournament, but it takes just one season for them to turn it around and win the cup. PSG is a very recent example of a club that can fail at a tournament multiple times and finally win. PSG has signed the best player in the world in recent years just to win the Champions League, yet they failed. They were finally able to win it last season.
I don't think Arsenal will win the UCL this season, but you never know. At the beginning of last season, no one would have predicted PSG to win the UCL, especially with the way they performed during the first half of the season. Football is unpredictable, and Arsenal winning the UCL is something that can happen.