Why can my opponent stop tds by backing up?

Why? Its incredibly frustrating shooting a double leg and i have to be right on top of them infront of the cage or else he cancels the takedown automatically midshot if hes not. Its unfair as hell when my opponent now knows im going to shoot and have ungodly takedown defense. Id rather have a poor setup up td that be defended easier then just stop and give my opponent a tell of what im gunna do. Please fix this 😞