I am not surprised at all about the situation of this game. Can't you see that happens with almost every popular developer? Excuse me but explain me that: How when they start to make the game, they are capable of releasing updates every month with low money incoming. But in the moment they got popular and rich they are not capable to release updates so early. The logic is: when you got money you update your equipment #PC, that means short time of renders, fast work.
It's because artist are not machines that you pour money into and then art comes out, like an assembly line.
In the fiction writing business there's something we call "Second Book Syndrome." Your first published book goes great, you have a lot of fun writing it, and you make some money off of it. But then, your second book is
hell: You're painfully aware of all the ways your first book could have been better, and you work much harder to meet not only your audience's expectations for quality but also your own.
On top of that, there's a ton of added pressure: If your first book doesn't sell, it's not a big deal, you've lost nothing but the time you spent writing it. (Most authors don't publish on their first attempt, it usually takes 3-4 before they get something that sells, sometimes much more.) But if you're successful and then your next book flops, that's your career as an author potentially gone.
(And if your second book is a continuation of your first, it's much harder to continue an existing story than it is to create a new story ex nihilo.)
All of these things combine to make your writing progress much slower (and much more painful) on a second book than on a first. And second book syndrome doesn't really go away on a third, fourth, or even eightieth book, you can learn strategies to cope with these issues but you never get back to just effortlessly creating like you did with your first work.