Well, this is an interesting thread…
I’ll throw my two turtles in then. I have not learned how to write kanji and I’m doing pretty well without it. Will learning to write kanji help with retention? Maybe. Will I ever learn how to write kanji? Maybe. I want to because it would be awesome and so I can say I can write Japanese.
However, my goal for learning Japanese is simply to read. That’s it. I have no plans to go to Japan or have conversations with Japanese people. I don’t intend to write a Japanese novel which would require me to recall what I know. Yes, I will probably learn some listening/talking skills simply because I will be absorbed in the language. I also know that my goals will probably change as I progress but for the time being, reading recognition is my goal and WK+grammar fulfills that purpose for me.
In reference to being able to read handwriting, I use this script. Obviously it’s not perfect solution, but it really does help with recognizing the kanji as strokes and not just the picture of a digital kanji.
I think that if you are not having trouble memorizing without writing them you will be fine. If you are having trouble, maybe just learn the one’s you get wrong on your reviews. It’s all up to you. Everyone learns differently and it can take time to figure out what works and what doesn’t. Anyways, just do you and experiment with different learning techniques until you find which one is less sucky. 
I bet you didn’t think such a simple question would cause such a ruckus 