How much more will the Arsenal team be underrated in the champions league even after they did exceptionally well in the premier league last season? They’ve just qualified for the champions league after their great performance in the premier league, let’s wait for the champions league to start before making assumptions on who is stronger to go far and those that will be eliminated from the first round of the competition. Every team is a star here after coming so far to reach here, so let’s see how the outcome of the group stage will be before we can at least start making speculations.
By the way, in the end, all participating clubs, except the finalists of the tournament, will be eliminated from the Champions League draw 
I would also not rush to premature conclusions about Arsenal. In any case, if the team wants to successfully perform on two fronts, then it is definitely necessary to strengthen the squad and, according to transfer news and rumors, the team is trying hard to do this. I don't think the club's management will set the task for the players and the head coach to win the Champions League right away this season, but it seems that at least Arsenal should get out of their group in the playoffs, although of course a lot depends on which opponents the draw will determine.