The version of your partner you first knew should not prevent you from meeting who they are becoming.

Long relationships build a working model of the other person, and the model saves time until it starts overruling the evidence. You answer for them, predict them, decide what they will enjoy, and rarely check whether any of it is still accurate. Meanwhile they have been changing quietly, sometimes for years, in ways they may have stopped mentioning.

Ask your partner something you assume you know the answer to. Listen for the parts that surprise you rather than the parts that confirm. Let the surprise update the model.