That is bad news. You just dismiss a Gemara like that? I would much faster dismiss something from the Moreh Nevuchim, like most of Klal Yisroel. The Rambam himself doesn’t use what he wrote there, in the Yad.
Anyhow, the Rambam starts off by bringing alot of Pesukim showing that everything happens for a reason. Then he says that this is only for humans – there is no Gezeira from Hashem specifically on any specific animal or leaf that it should fall or be caught. Then he goes on to say that since the special Hashgacha is due to the Sechel, it follows that the more you got the more Hashgacha you’ll have. For an example, he mentions the special Shmira that the Avos had. Then he mentions that Risho’im lose their Hashgacha, they lose their Shmira, and will certainly get hurt soon enough. What you wrote here, to someone else, is the outlook that the Rambam attributes to Aristotle.
What the Rambam writer about Risho’im is nothing new. It is a Pasuk, Vehelachtem Imi Bakkeri… This is also with Din. It is in fact what Chazal say about Mipi Elyon Lo Tetzei Haraos. Whenever something bad happens, it wasn’t Hashem’s hand punishing, it was Hashem leaving the culprit alone.
If what you say is true, we wouldn’t make a Birchas Hagomel. You would have to thank Chance instead of Goodness.
Another point: The Mekubalim say that even what the Rambam says is a Mikre, is also from Hashem. This too is not necessarily refuting the Rambam’s words. They also would agree that there is no Gezeira on each leaf. Being, though, that Hashem made the world and its weather and all the randomness comes from Him. So the idea is that ever thin that happens is Hashem’s plan. Even, and especially, the Mekubalim agree that there are Mazalos at play. Yet they still say that everything is from Hashem.