Considering that a decent blue eyes deck can win against Yubel when Yubel is supposed to be the counter of Beatsticks like blue-eyes, perhaps the other guy is right.
Didn't try Yubel deck for myself though, so I can't be sure of that.
Unfortunately, many Blue Eyes decks tend nowadays to tech Stardust Dragon (Cosmo Brain + Lv 1 Tuner), which alone can easily counter an entire Yubel deck.
Nope, Ultimate Nightmare cannot inflict damage against Stardust. Stardust will negate and destroy it instead. You need Cerulean Sacred Phoenix to take out Stardust. I am veteran Yubel player, got KOG multiple times with Yubel but I must say Yubel is trash in 2020