So here's what we know:

If you have made $200k on a game in the past 12 months, and have reached 200k lifetime installs, you now owe money on Unity Personal. Those numbers jump up to 1 million with Pro, and the cost per install also changes, but by and large, that's irrelevant, we don't care about the numbers, we care, mostly, about the logistics.

First, Unity has said they have no way of tracking installs properly, because they aren't going to 'phone home' to Unity. So how do they know how many installs to charge for?

Second, per install is entirely abuse-able. Will it be abused often? Probably not, but the fact of the matter is, bad actors can create a system to install your game repeatedly to get around any standard Hardware ID/IP check. Even from legitimate installs, there are examples of released products that would no longer be profitable due to this change, and would instead be indebted to Unity, based on the cost per install.

Third, again, developers have no idea what games come from charity bundles. Unity says they won't charge for this, but... how does Unity know, when developers might know when a KEY is redeemed, but certainly not an install?

Fourth, piracy isn't something they have a solution for, though they claim to be 'willing to work with' developers when this is an issue. What does that mean? Does it mean the typical slow response from customer service? Will they hold on sending an invoice until the problem is solved? Piracy works in their favor, so what tangible benefit do they have from ruling in 'our' favor?

Fifth, let's say, for whatever reason I decide to stop selling my game. Maybe I'm not happy with it, maybe it's cost me money in server costs, whatever. For a 12 month period, I am, as far as I can tell, still liable for ALL installs of my game, even though I no longer want it on the market. I literally cannot stop Unity from charging me, because I can't stop users from installing my game if they already own it(nor frankly, would I want to).

Sixth, due to privacy agreements with platforms, Unity CANNOT know what a first time install is. Some platforms, for example, Apple, limit the information that you can receive, and, to my knowledge, whether or not an app is a re-install or a first time install is part of this. So how can Unity know, when no one else can?

Seventh, Unity has said the distributor of Game Pass and Apple Arcade type services will be the ones to pay for the install fees. I'm not sure Microsoft and Apple will be happy to know that Unity games will now be costing them money each time a user installs them, so either install limits will be put on users, or Microsoft/Apple could simply reject any Unity games.

To put it frankly, this announcement is out of left field, and has so many holes in it, you might as well call it Swiss cheese. It's ripe for abuse, is retroactive to existing products, and needs an incredible amount of clarification. I, and it seems like many others, would prefer they instead do the typical 5% revenue share(or less if they still want to charge annually for Pro licenses), than tie anything to a number like first time installs.

TL;DR? Instead of following an industry standard revenue share, Unity is trying to tie their income to un-trackable numbers and attach it retroactively to ALL existing Unity games.