WOW! Well said, Catherine!
I think you just answered your own question.

Without love, emotional intimacy and vulnerability true love cannot exist. We can only love to the depths we allow ourselves to be seen.
I have read a lot on how men cannot even fall in love without the vulnerability of a woman in play.

The vulnerability is what makes us really feel the deep love and stay in love.

So you two were so right for each other in many ways but that was missing.
You are on the right track because you instinctively knew that something was missing.

To see if this indeed was the missing ingredient you could ask to see him and open up and be very vulnerable with your feelings.
Tell him how you REALLY feel.

If you don’t want to do this, then just work on opening up in the future.
I wish you well.