Yatsenyuk was complaining and raging a lot before his resignation... I'd say for a whole list of good reasons. State "treasury chest" is empty. No money to pay soldiers and police. No money to buy new nor to repair damaged weapons. No money to pay people in health care and education. Gas and oil storages empty. ATO is running sloppy and slow. Losses are much bigger than anticipated and growing expenditures are becoming unbearable. Parliament blocked in complete chaos. Government full of amateurs. President doesn't know how, or doesn't dare to use his legal authority on anything. Potential western allies are blackmailing, like in "hand us 50% of your gas and oil transportation network and then we might think about helping you. Sometime. Maybe. Or not".
Since Ukrainian economy right now is being controlled by the IMF, they can't just print more money as any truly independent state would necessarily do in the case of war to finance their growing military spending...