Yes, and I went to the final, that too with a team of around 98-103 % only. So, it is possible to knock-out those teams. And also, you are right about not selling your 7-8 star players. Why a user will make so much effort to get such players, only to sell them at the end of the season and to get a better cup draw but inferior competition?
But some users don't see themselves be able to deal with such situations or to take the challenge, and so they choose the easy way. But, it is understandable that a user might once do it if he was never able to win the Cup due to being put with teams that are in the levels above every season for say 6-10 seasons.
To each his own way of doing things, but I don't agree with what some do. Some users choose the easy way, and yet come and show off as if what they have achieved are due to their football managerial and tactical skills. Some even show-off on YouTube. The same applies to some of those users that used 'tanking', and then show-off without mentioning that they have tanked for one or several seasons before.