Basically, everyone always focuses more on a team's strength and ability in any competition because surprises are something that no one can clearly predict, even though they occur every season in the Champions League. However, it's still difficult for anyone to make predictions based on other aspects because the true strength and capabilities of the big teams entering the Champions League have yet to be revealed. Therefore, everyone will have to wait and see who the strongest team is in this season's Champions League.
We all love to see underdog win but we usually talk about big well known teams first. It is normal to favor what we already know. Surprise teams that do well in Champions League are remembered because they go against everyone expectations.
You are also right that we do not know how strong top clubs really are yet. At start of season teams are still getting used to each other new players are joining in and they are working on their game plans. Due to this beginning of tournament so interesting. We can not know who real favorites are until later and like you said we just have to wait and watch to see what happens.