Now it makes sense to say that previous matches and consistent performance in the Domestic League cannot be completely used as a benchmark, because playing in the UCL is very different. Of course everyone was shocked by Arsenal defeat to Lens, and it is evident that surprises happen more often in the UCL. Even though on paper Arsenal has a better chance than Sevilla, that doesn't mean the opposite can't happen, but if you look at the statistics, Arsenal should be superior.
Even though I'm not really sure Arsenal can get 3 points this time at come to Sevilla, I don't think they will lose that match. Sevilla has an advantage because they act as hosts, then they have to create their own luck while hoping that Arsenal doesn't play well so they can take advantage of it, because whether they admit it or not, Arsenal is still better than Sevilla.
Indeed, on paper Arsenal are clearly superior in every way, but because this is the Champions League where the prestige and tension of each club is really at stake to minimize losses. Sevilla is quite bad in the domestic league but still playing against Arsenal is a challenge for them, playing at home is a plus while the mentality of the other Sevilla players must be proven in front of the supporters. On the other hand, the visiting Arsenal team should be able to control themselves and not be easily provoked, considering that Sevilla will try to provoke their opponent's emotions so that their focus is broken and they can control the game. For me personally, the possibility of Sevilla winning is quite difficult but there is little hope that they can win with a narrow result.
Of course, in the Champions League, it is difficult to predict for the teams competing in it, apart from the very competitive tension of the matches, they also bring the pride of their respective domestic leagues to the table, thereby also putting the reputation of their domestic leagues at risk.
What makes it difficult to predict in the UCL is because they come from different leagues which makes it difficult for us to determine the probability of which team will win when they face each other, because we can only look on paper and see the popularity of their respective domestic leagues.
For Sevilla itself, they have played twice in the UCL to get points from a draw, and yes we know that every team will focus on getting the best position in the UCL, even if their domestic league has a bad performance, when they enter the UCL match they will be very difficult to predict.