I think the key problem is that most game developers are broke and most games are unsuccessful if they even ship.

The "picks and shovels" business model where you build tools for customers who use them in their own enterprises can be very successful. But it does require those customers to be successful in their enterprises. (Or you can rely on customers to be willing to pay out of pocket at a loss because it's a hobby, as with music instruments.)

Without some kind of other monetization, Unity is essentially selling picks and shovels to miners on a mountain with almost no gold in it.

To be clear, I don't think this justifies what Unity is doing. But they are clearly trying to be a $$$$ business in a $ market, and are willing to sell their souls to get the extra $$$.