Q: What do you do when your immediate supervisor (an assistant manager) never takes a stand, never provides feedback or reactions to your work, gives you no support, and provides no leadership?
A: Have some compassion. This manager clearly has low self-esteem. Think about his relationship with he superior. He is probably avoiding taking any strong positions because of the negative feedback or lack of support he has received from his boss.
You need to take the initiative. Don't let his inertia block you or your department's progress. If you want feedback, ask. If you want to move on a new project, present it as fully and carefully as possible. Make it too good for him to object. He sounds just passive enough not to block you.
Sometimes, you can go ahead without permission. In most bureaucracies, it's easier to ask forgiveness than to gain permission! Neither the boss nor the company is likely to kill you for being
aggressive, even though they may not have supported you if you'd asked for their approval.
Maybe you could even take on some of his responsibilities. Let him know your slate is clear, that you could handle project A. Or ask him if it might be helpful for you to work on project B. Let him know you're there, that he can count on you, and that these projects need to be done.
You might also try teaming up with other departments, particularly ones with more proficient managers. Dream up projects you could work on together. It'll be good for the company, satisfying for you, get your efforts recognized by others in management, and eye-opening for your boss. Good luck.