Cups left on the table are more so the result of poor drafting (Connolly, sorta Namestnikov, Koekkoek, sorta Drouin, DeAngelo, both Foote brothers, (especially Cal) and a bevy of 2nd rounders like Blujus, Hart, Erne, Masin, MacLeod, Stephens, Spencer, Katchouk, Volkov. Howden and Hajek were turned into McDonagh & Miller, but both were drafted ahead of DeBrincat, which was bad. Katchouk was turned into Hagel, but he was drafted ahead of Girard and bad luck (Bishop, Stamkos, Point all getting hurt in separate instances during the playoffs and/or regular season)
The only Cup that should have been an "easy" one was 2018, and I place that on Cooper for failing to adjust when Trotz definitely outcoached him in the Conference Final. While 2019 was embarassing, that was a 1st round series, no guarantee that they get to the Final even if they beat Columbus.