You can fall in love with the IDEA of someone by text and can get huge insight into their personality, likes, dislikes etc. It's a great first step and very foundational.
But you need to feel the person, smell the person, listen to their voice, hear them laugh,watch them eat, see how they treat others and relate to their family, service staff when at a restaurant, how they drive, what annoys them etc. All of these things (and more) is what makes a dynamic work.