It is a mystery
Tory Lanez Stan
inshiki Otsutsuki from Boruto the movie has the power to split a planet according to the databooks and he's weaker than Madara.
This tree is so large that mountains look like grass compared to it
Toneri from the Naruto Last Movie cut the moon in half and he's also weaker than Madara. He also was about to destroy Earth by ramming the moon into it. Don't forget that Naruto took that moon attack to the face and it didn't affect him so it probably would damage Madara as well. In that same movie, 50-100 ninjas were focusing their chakra into a cannon to completely destroy the moon. Madara has more chakra than 100,000 ninjas. No matter you look at it Madara has the power to destroy a planet easily.
He literally covered the planet with two of his jutsus without sweating (infinite tsukuyomi and the tree that had spread its branches all over the world). That feat proves that Madara can easily make the planet drown in water or put the whole surface of the Earth on flames easily. He didn't destroy a planet because he was trying to make a "peaceful" world.
Madara is stronger and faster than Aizen. If you read my previous arguments you would already know that Aizen's hypnosis will not affect Madara because of his sage mode (extremely powerful sixth sense) and Aizen's ability only controls the 5 senses.
Outside of the bortuo movie, most feats in naruto are small in terms of pure destruction. Madara being a planet buster was never a thing in the manga/anime and none of his attacks demonstrated enough impact to eradicate even continent, let alone a planet. Only if we powerscale him up from the otosuki clan does he even get to being even moonbuster level. If Madara really was a planet buster, he would have stomped everyone immediately.
The God tree is not the size of a planet. It's supposed to be naruto's version of the Yggdrasil tree. Neither tree is the size of planet. They are just big trees.
The biggest feat in Naruto is slicing the moon but the moon =/= a planet like earth. Moons are nowhere near a planet in scope, especially in fiction. Also Kinshiki Otsutsuki is even with sasuke by all accounts (every wiki, what happened in the manga, etc.) and Sasuke isn't blowing up planets either.