I'll give you a chance to fight numbers as well.
Attack that wasn't good enough last season scored more goals in PL (77) than in any of the seasons Mount, Havertz and Werner were here 69, 58, 76, 38.
I disagree about what is harder to win. If you win PL you are undisputedly best team in the league.
In CL it's easier for surprises to happen.
How do you explain that we won CL while finishing 4th and 6th in the league? Spurs reached final while finishing 4th in the league. PSG reached final without facing top10 teams in Europe. Dortmund, Atalanta and Leipzig was their road. They lost finals but in one game off anything could happen. Early penalty, red card... So easy draw, a little bit of luck and you have a chance. In the league you cannot hide under those things. Lyon eliminated City while finishing 10th in Ligue 1. We all know City wins 9 out of 10. I can maybe agree that for absolutely best teams it's easier to win league than CL because you have no place for mistake but we were not one of those. That's why we couldn't challenge City in the league but did won final.
From Werner I remember horrific finishing so how is that strong mentality? Once he miss one big chance he is done. Also I don't remember excellent performances from Mount in the league. In his career he played around 60 games against traditional big 6 and scored just twice. One was DDG howler in Cup. Most of his goals were against 5,6 worst teams in the league and assists from corners. Easy to check.