Usually a chance to participate in the champions league for those who aren't regular appearance in the champions League, it's regarded as an honor because how els would they have an opportunity to showcase their skills on a level ground with bigger teams of a very high world class standards outside their domestic leagues if not for the champions League and that could be one of the reasons to its prestigious nature. I don't know what it feels like you have regarded Arsenal as a stronger opponent than Liverpool against Atlanta in the champions League, I want you to remember that Liverpool is even more consistent in the champions league than Arsenal and are even more experienced than Arsenal so they are the biggest for me, if it were to be in premier league then I would consider that really differently.
Hey I have checked the matches that Atalanta will play in the Champions League where they do not have a schedule to face Liverpool in the first round. Just check the match table where in 8 matches Atalanta only faced Arsenal, Shakhtar, Celtic, Vfb, Young Boys, Real Madrid, Strum and Barcelona. So the strongest opponents that Atalanta will face are of course several teams so they have to really focus if they want to advance to the next round.
On the other hand Liverpool is also very strong because so far they have shown an increasingly improving game under the guidance of Arne Slot. So there are many matches that they will play in the Champions League this season, I hope Salah et al can bring many surprises by defeating their opponents.