I explained my reasoning many times. If he is stronger than that, it's Oda's writing which is at the wrong.
Last time we saw Lucci he lost to pre Haki pre Gear 4 basically fodder Luffy for New World standards.
Lucci was confirmed to have Haki at that point which only makes it look worse and mind you, Lucci wasn't training hard as fuck for the last 2 years but he was on the run until magically Oda included him back to CP and now CP-0
I can dislike this choice. I'm in favor of old characters improving from their defeat but not in a shitty way where their power-ups/power level improvement is basically a handover/ass pull.