Not replying is a reply. Just make sure it’s the one you meant to send.

Silence gets read, and it gets read as a decision. The other person does not know you were busy, or waiting until you could write something good, or simply forgot, so they fill it in with the least flattering explanation available. Weeks of nothing says something quite loud, and usually not what you intended.

Go through anything you have left hanging and send the short version today, even very late. Two lines beats the perfect message you were never going to write. Where you actually do mean the silence, like with somebody who keeps asking for things, let it stand on purpose rather than by accident.