In general, Real Madrid is still able to survive in the UCL because luck is often on their side, including when facing Atletico in the second leg. At first I thought Madrid would be slaughtered after Atletico took the lead in the 1st minute, but after that Atletico were unable to increase their lead even though they always built fast attacks that troubled Madrid's defenders. There is no doubt about the mentality of Real Madrid players, but they still have 4 games left before reaching the final.
In the Champions League, Real Madrid, in addition to luck, also has the support of the referee, because this team often plays as champions, so in some controversial issues they get an advantage, even as it was in the cancelled penalty of Alvarez, in my opinion it is stupid to cancel such a penalty... So in order to beat Real Madrid, you need to be not only stronger than them. You also need to take into account other circumstances that can affect the result and in the case of Real Madrid, it is not only luck.
Many will think the way you are thinking is not really that Real Madrid are been favour by ref, though sometimes the actions of the ref in some game one will probably make some think that the ref is against the other team but sometimes I see it as the action of the ref we are human being as the as those ref so they can makes mistake sometimes when officiating games because they are also imperfect humans, Real Madrid is always lucky when it comes to the UEFA Champions league sometimes they have to win their at the last minute of the game, some during extra time, some also they will win after penalty shot out, some most time in other to defeat Real Madrid you need to start winning with a good goal margin so that before they can pick up and start doing there miracle it will be too late, but let the honest truth be told Alvarez penalty should have stand I don't really know why the ref disallowed that goal I have watched to game severally Alvarez left foot never touched the ball as the ref May clam but the deal has been done.