Why Fujitora's feat compared to Kaido's leaves Kaido at the advantage:
1. Fujitora's rubble cloud is very light compared to kaido's feat. Sure Fujitora's cloud covers an area about 10x as expansive, but since it lifted up exclusively buildings, the cloud fundamentally proves to not be dense. Kaido's Island is almost as deep as it is wide: that's more than a Kilometer of bedrock lifted off of the ground. Aka, over 100x more weight for each portion of area lifted up. Even if the city of Dressrosa occupies an area 100x more massive than all of Onigashima (which itself is significantly bigger than Marineford), Kaido''s feat would still weigh more.
2. Fujitora's rubble was lifted using "gravity manipulation", not "power". Aka, if it was sturdy enough to hang upside-down, Fujitora would not be able to lift it off the ground like he did the rubble. Thus, for most Islands, even if he covered their entirety with his gravity field, a feat like Kaido's is still likely impossible. The actual "ripping out of the ground" being too hard for him. Thus, Fujitora's is more situational. Also, Kaido created the clouds which cause Onigashima to lift by physically pushing it upwards. The amount of lift force necessary to do this, with as few clouds as we see him use, could seriously launch people ludicrously high, with ludicrous force, thus, it's likely got more deadly combat application than Fujitora's fruit which merely forces their opponent to fall upwards through reversing or undoing a gravitational constant.
3. Fujitora's Gravity that allows him to lift rubble is his sole claim to admiral level. In case you didn't remember, Fujitora's CQC is basically Tobi Roppo level, if even that. A still-bandaged Gear 2nd/3rd Luffy was giving Fujitora trouble in their fight, and had an easy enough time to call out the names and descriptions of all of his attacks while doing it. Zoro, who wasn't even angry at Fujitora yet, was enough to make Fujitora quake. And sure, Fujitora occasionally pull down meteors as well, but those can be dealt with rather casually even just by the likes of Doflamingo and Dressrosa Law, or dodged by fodder Marines. Without that rubble feat to give us the benefit of the doubt, Fujitora wouldn't even register as high as Yonko Commander 1, to be honest. Meanwhile, Kaido is not reliant on his lifting ability at all: it's just a bonus. The guy has top tier stats across the board regardless. There were threads of Kaido vs Fujitora, where the general consensus was that Kaido obviously won, even just the week before the chapter came out, when we had no idea kaido could do anything like this at all.