Although if Lucifero loses. I think I will sayy goodbye to this manga.
Since that's clearly going to happen on some level in the next few chapters, your ultimatum here seems pretty cringe to me.
As bad as you might think this writing is, the necessary players are definitely present to allow for 50% Lucifero's logical defeat. Especially if he stubbornly refuses to use magical attacks or use magic in any sort of interesting or hax way (like we know he can through Dante).
William has always been this sort of black box of unknown potential, especially since he was potentially going to be the next wizard king after Julius, so a sword that supposedly has "All of his magic" in it, is definitely no joke.
Yami has of course, also been somewhere near top tier as well, fighting evenly with Dante, even despite his relatively low mana level. And now, with recent chapters, it appears that he's gotten a really significant mana buff (by turning into a demon biologically) along with a sword that's also given him a significant mana buff, and since mana skin (which Yami knows) can translate mana into stats, Yami has logically received an absolutely ludicrous stat buff as well. Him being on a similar level of effectiveness to Yuno against Lucifero only makes sense. And given how Yami's magic can ignore durability, the tiny slash that he made on Lucifero would've made sense regardless of his buffs.
As for Nacht, he's finally received the character development to not be suicidal, and as we know, character development means power-ups in Black Clover. And he was already Triad level before as well, while only using one of his devils at once for union, unlike two, which he does in this chapter. And the idea that Dark magic and Shadow magic have insane levels of synergy is obvious as well, since one of them teleports but doesn't do much damage, and the other ignores durability but inherently moves really slowly.
And the final thing that you've complained about, Zora being able to stall Lucifero for a few seconds, is basically just what Zora does. Zora's trap magic is entirely about catching masses of mana (regardless of how big they are) and reflecting them with multiple times the previous force. And sure, maybe you're protesting because Lucifero came as Zora with a simple punch, but you'e got to remember, Lucifero still isn't fully manifested on earth
. If we're thinking about it logically, his entire body is merely mana right now
Black Clover is great, and it's been great
. Lucifero needs better feats, definitely, but that's hardly a unique problem and the scaling is all there and all makes sense right now.