I agree with you, I believe Arsenal are a good team but they are not yet the team to compete in the Champions League and win the trophy. They might not fare too well against tough opposition in the Champions League. To do well in the Champions League tournament or to secure the final, the best performance is required and we may not be seeing that best performance from Arsenal right now. We could see PSG with Manchester City Real Madrid Bayern Munich in the semi-finals of the Champions League.
When Chelsea won their first Champions League about twelve years ago many people never believed they would make it to that level. They just sacked their coach and appointed an inexperienced Roberto Di Matteo after sacking Villas-Boas. But the team was united and made it to their first-ever Champions League title. Arsenal have a good team made up of both young and experienced players. Mikel Arteta has been able to motivate these players to become warriors. They might not be as exposed as other top teams but I dont doubt their ability to come up with some surprises. If they have luck behind them, we might see the Gunners in the semi and even the finals.
I think getting a trophy is not just a matter of luck because of course, to achieve the highest achievements requires good consistency too. But indeed, Arsenal this season is quite impressive and as such, Arsenal will have a chance to progress further even though it will not be easy at all. Apart from that, to achieve the highest achievements of course they will need a good mentality and if Arsenal doesn't have a good and consistent mentality then at least it will make it difficult for Arsenal to advance to the final match. But for me personally, because Arsenal has managed to qualify for the quarter finals, of course that is still a good result and it won't be a problem if in the end, for example, Arsenal loses in this phase.
Luck is the final reason for any club to be able to win the Champions League title and the main reason, as you said, is the quality of the players' performance which is very influential in being able to continue to survive until the final round.
Support from experience is also one of the reasons a club can win a title because experience can provide strategic assistance that can be rearranged when playing against a particular club to achieve a winning score.
Of course, Arsenal may be consistent, but in terms of the quality of performance of Arsenal's players, they are not very strong if they have to play against equal clubs and I may have little hope for Arsenal and still believe that Manchester City will be successful this season in winning the Champions League trophy.