Working with unity is gonna be kinda hard after the new policy
You need to get over two thresholds. Downloads alone are not sufficient. If you have over $ 200k in sales for your game, you have other things to consider as well, like paying taxes, having a business etc.
I am more concerned how they measure the "installs". And they specifically speak about installs. Not downloads. Most, no, every game I saw on itch is not an installed game. It is unzip and run. There is no installation routine. So no installation process. And not even considering web games at this point.
How exactly does Unity know, if and how often a game was installed?! Are unity apps phoning home? When? If it is not at installation, as there is none, it would have to be at each start. Wich would mean, they would have to have a database of users to distinguish returning users and new users, as they plan to charge for installs. That breaches privacy. I have a contract with the developer, not with the engine maker. I did not allow Unity to collect my data. They might even violating data protection laws in several countries with this.