You are not sad because you have not moved on.
Your feelings are not blocks that you can pick up and deposit in a different bucket when things aren’t working out, you can’t move them from “loving you” or “missing you” to “completely indifferent” no matter how much you want to. It has to come on it’s own and you are not a failure because you cannot control the pace.
Sometimes we’re with someone and it feels like love and magic, and we learn for them it never felt that way at all. It’s easy for that person to get over you, somehow you really weren’t to them what they are to you. But that doesn’t negate your feelings, it doesn’t invalidate them. No matter how much or how little the other person cared for you, your feelings for them are separate — you’re not the kind of person who loves in small doses, contingent upon how much you are receiving in return.
The love you still have, the memories, are not pathetic. They are a testament to your ability to love someone else more than they love you. It means that you are not stingy, not a miser, not someone who waits around for others to do the work of making a big love.
For better or worse we are not in charge of our feelings, we cannot order them around.
If the world wants to tell you something is wrong with you for something you cannot control, fine, let them. But your truth is that the markers left by a relationship only show you how big your love is, how uncompromising, and nothing is a better predictor of future romantic success than being able to give this kind of generous, no-strings-attached kind of love.