The more the series goes on, the more I think that Zoro actually might have gone all out in Dressrosa. Not that Asura magically doesn't exist post skip, but rather that Zoro asura is an unreliable power up.
In enies lobby, Oda introduced power ups for all of the m3. The gears for Luffy, diable jambe for sanji, and asura for zoro. However, out of these three power ups, it seems as if Asura is the only one that Oda is treating specially.
Asura seems like the most elusive power in the series. It was used only two times in the manga, and both of them happened pre-skip, effectively 10 years ago in real time.
In thriller bark, we see Luffy use the gears and sanji use diable jambe, but no asura from Zoro. Then post skip happens and we see Luffy with improved G2/G3 as well as G4, Sanji with improved diable jambe and hell memories, but we haven't even seen asura. It seems as if instead of mastering asura, Zoro instead focused on mastering his physical strength and haki, as his high end moves using black hardening can arguably rival G4 in terms of attack power.
So why no asura? According to Zoro fans, its because Zoro is simply too good to use asura. He is so all powerful, that he doesn't even need to use his full strength to defeat powerful enemies. While this argument might be fun to entertain, especially if you are a zoro fan, I feel as if it is a bit biased and lacking in insight. We are to believe that Oda would go 10 years without showing Zoro, one of the most popular characters, use his true strength?
I just don't see the logic in this. I don't get what's the point in making us wait so long. Doflamingo was hyped since pre-skip, there is no reason why Oda couldn't have made Zoro go all out in dressrosa. There is no reason for Oda to prolong this moment.
So here is my theory. To the dismay of Zoro fans, I think it is very likely that Zoro went all out in dressrosa. The reason for this is because I speculate that Zoro 1) doesn't have control over asura and 2) never did have control over asura.
from our observations, we can see that asura is used very infrequently. I mean it was never used in Thriller bark at all. This obviously wasn't because Zoro didn't go all out, as Oars was stronger than all of the straw harts combined, so was moria. Zoro was even temporarily knocked out one or two times. Oars was so strong that Luffy needed to use nightmare luffy to defeat him and then go G2+G3 to beat moria. So why didn't zoro just use asura? he had absolutely no reason not to, especially when kuma showed up.
And I think you can make a similar argument in dressrosa. If Oda was going to give Zoro the enma training as a power up in wano, why didn't he show zoro's full strength in dressrosa? Wouldn't it make sense to see Zoro use asura at least once in 10 years before having him surpass his limits with the enma training?
I think the answer is simple. Zoro doesn't know how to use asura. Even if he's pushed with his back against the wall, there's no guarantee he will be able to use asura. This is why Zoro's non asura atttacks are so powerful, why he created new moves like ISDS and rengoku oni giri, rather than mastering asura and learning how to use asura casually. Zoro simply wasn't able to control asura.
While many people might laugh or troll at the idea that Zoro went all out against pica. It isn't actually without precedent. There is very strong evidence that both Sanji and jinbe went all out against wadatsumi, who parallel's pica in that he is also extremely large. Sanji stated that he used his ultimate attack in fishman island and vagabond drill was the same attack jinbe used against big mom(where he had absolutely no reason to hold back).
I think it could be that rather than give Zoro, Sanji, and jinbe strong and serious opponents in the. new world, he instead had them go all out against goofy giants that are hard to take out.
And as for why Zoro cant use asura on command. I think it might be due to the sandai kitetsu. The sandai is the weakest kitetsu after all. If asura is from the kitetsu, maybe zoro needs a stronger kitetsu sword, like the nidai, before he can fully control asuraa.