You sound like Arsenal doesn't have players and they are not good, I won't be surprise if Arsenal beat Real Madrid because anything is possible in football just that Real Madrid always play with a special spirit and mindset when it comes to champions league and they are always fortunate to win or qualify. Arsenal has two strong midfielder Declan rice and Martin Odegaard and Bukayo Saka is back from injury though he is not that strong but I believe he will don wonders that day. We should not conclude or be so sure that Real Madrid has qualified because the outcome is not certain.
Arsenal also have great players who can give them a chance to achieve better results, but we also have to consider experience and mentality because talking about the Champions League is different. The last time they met was when Thierry Henry was still a mainstay and Arsenal managed to beat Real Madrid but that was a long time ago and maybe the quality of Real Madrid is more mature now.
I remain optimistic that Real Madrid will finish the match to qualify for the next round but I will not underestimate Arsenal's ability who might provide a surprise because the first leg can be a little more favorable for the team that is able to win the match.
Arsenal will only try their best to see how they can outsmart Madrid but it wouldn't be easy, because Madrid attacking pressure will sweep them off their feet. Real Madrid is not going to allow any laxity from their side that will make them not qualify to the semifinals. I feel this is end of road for Arsenal in this competition.