Is it easier to win the CL now or was the old format European Cup easier to win?
In my opinion the CL is harder, yes you can afford to slip up once or twice but then you could do that in the knockout format too once you won the second leg. But now you have more teams coming from the strong leagues where in the past it was just one from each league and although seeded at early stages, it was more likely that 2 large teams could meet at an early stage.
Generally, though not always the case, it is likely that you will get the best four teams in European in the semi finals than with old format.