I pretend to ask for input when I have already decided. How do I stop?

You already know it rings false, and so do they. Fake consultation is worse than no consultation, because it spends people's time and their trust at the same time. They give you a real answer, you nod, and then you do what you were always going to do. After a few rounds of that, they stop believing anything you ask is genuine. The good news is the fix is simple, even if it feels exposed. When a decision is made, say it is made, and tell them why. When you truly want input, ask for it and be willing to let it change your mind. People can handle a leader who decides. What they cannot forgive is being used as props in a performance of listening. Next time you catch yourself about to stage a consultation, pause and name the truth instead. Say plainly: this one is decided, here is the reasoning, and here is where you can still shape it. That honest sentence will earn you more respect than any amount of polished, hollow asking ever did.