How can you say he'd be equal with nothing to prove that? I understand you're a Lucci fana and Lucci is without a doubt YC1 level but let's no delude ourselves just because Luffy easily beat Lucci in Gear 5 doesn't mean he can't beat him high/mid diff in Gear 4.
Gear 4 AdvCoC Luffy > Current Zoro >= Current Lucci
But that is the problem, Luffy did
not easily beat Lucci in his Gear 5, in fact he did not beat him at all. Lucci did immensly well for facing and fighting Gear 5 for his first time, even having an equal clash blowing each other away! (edit: dont forget how Kaido did in his first encounter with gear 5)
But since the moment Lucci focused in killing Sentomaru, it was no 1v1 fight anymore, but Lucci trying to kill Sentomaru and Luffy butting in from the side trying to protect Sento. Lucci even managed to dodge one of the attacks.
At the end Lucci was
far from defeated and Luffy escaped for other reasons (letting Sentomaru whom he tried to protect even behind him). During the entire encounter Lucci did
not use a single named attack on Luffy - the one named attack he used was on Sentomaru and that was strong enough to one shot him through his barrier and fast enough for Gear 5 to be unable to react.
Lucci proved well enough that there was a
reason Luffy decided to go into his strongest form immedeately. Lucci proved he is not Yc1 but a level above, so basically in between Yonko and Yc1 - and that is where Luffy without Gear 5 is as well, Kizaru basically proved he aint Yonko/Admiral level in even Gear 4, let alone Gear 2/3 and base.
I could probably agree to:
Gear 5 Luffy - Mid/High Top Tier
Gear 4 Luffy - Low/Mid Top Tier
Base/Gear 2/3 Luffy, Lucci, Zoro - Low Top Tier