No, you're quite right, and I didn't mean to imply that the system was changed because of the class IR. I do believe, however, that the fact that we had the class IR by that point informed the design of the new system.
It begs the question, though: if it never was a problem for all these years, why is it now?
I have to say that, while I supported the change back in the years, with hindsight, I think it was a huge mistake. The communistic system is a lot more fun. The new system creates way too much income disparity, with most knights not having the funds to recruit as much as they could, a good portion of nobles depending on a meager income from a border/unpopulated region for months if not years before said regions become productive, and city lords that gain ridiculous incomes, way more than they need, and that often hoard it even during war time. Overall, armies are funded much more poorly than before, which limits the potential for war, and makes a lot more wars into stalemates as realms have a hard time funding large enough mobile forces to counter enemy militia in fortified locations.
