I agree with you Real Madrid has a lot of experience and plays well consistently so they have good chance of making it to next round. PSG has been playing very well lately and they might be able to overcome their next challenges and move on to next round. Manchester City does not play well all the time but if all their players do their best they have enough good players to make it to next round. You are right getting out of the group stage is not that hard for big teams but teams they play next will be even tougher and that is when it gets really challenging.
Real Madrid players have a lot of experience and it is true that they perform consistently but they are not able to express their experience in the UEFA Champions League. But in La Liga they have managed to maintain their consistency even though they are already number one there. None of the three teams you mentioned are performing well in the Champions League at the moment. Manchester City has played 6 matches in UEFA Champions League so far and PSG football team has also played 6 matches. Both these teams have the same match win statistics, we have seen that they have managed to win only two matches. Therefore, according to such statistics, no party can be considered as strong. So it will be more difficult for them to go to the next round.