Let's do some math. Next year the clear favorites for the PL will be Man City and Liverpool. You could easily say Man City have about a 45% chance of winning, Liverpool about 40%, and Arsenal, Man Utd, Tottenham and Chelsea each about 3% chance. Those are pretty good odds for Man City and Liverpool.
In the CL, Man City and Liverpool are probably 95% sure of getting through the group stage. After that, though, it gets tough because there are usually 6 or 7 clubs who could beat you on a given day. The favorite might have at best a 20% chance of winning once the knockout stage starts. That's 1 out of 5 versus almost 1 out of 2 for the PL.
Man City have arguably been the best team in Europe the last two years and have not even made it to a CL final. The odds are against you no matter how good you are in the CL.