My main concerns are around losing time, attention, and specialness. I have told her when I feel excluded, and she has struggled to not react defensively in those conversations. She often is not as proactive as I would like to make me feel special, despite the fact that I have told her that I need that from her.
I keep finding myself asking the question, "What's in it for me?" Marriage is a give and take, and I feel as if I am giving so much and not receiving much from her in return.
I find it interesting that your concerns don't sound like you're afraid of losing her, or of being replaced. As those are often fears too in poly, I'd like to ask if any of those come into play for you?
For the things you cite, those could all be combated by a combination of you working on them, and her working on them. Ways that YOU would work on them including thinking up actual, concrete activities/rituals/words that would valid that she does feel that you're special, is giving you the kind of attention you need and spending time on you. Another thing that can be important to do is acknowledge when she IS giving you those things, and not less a little voice of negativity devalue those things. For instance, when my partner was dating me and Lora (his ex), they would often hang out in our home, whereas he and I would go do things, or do a specific activity together: play a game, read to each other, cook together. Often, Lora would devalue the time that she and Jon spent together, saying it "didn't really count" and that he obviously liked me more, because we did stuff together, whereas they "just hung out".
So, if (for instance) some of your feelings of time and specialness involve doing something other than "just hanging out", it would be on YOU to start thinking of things to do other than "just hanging out". That's also something your wife could help you on. Are there things that you've said to each other, over the years, "I'd love to do X", but you never did it? What if you started doing those things? Or found other things you've never done and would like to do together? Are there things that you've always wanted to do alone, but you never did, because most nights were "just hanging out" with your family (note, I don't think there's anything wrong with "just hanging out" but sometimes we get into a rut of always "just hanging out" instead of doing things that nurture our soul or our intellect)? Those are things you could do when she's out on a date, if you have no interest in poly for yourself.
As for "What's in it for you?" what do you want to be in it for you? What *could* be in it for you? More free time, to pursue those interests that you never got into before, because there was never time? Do you want to try dating yourself? Do you want to spend more time with your friends, or your children, or volunteer? What's in it for you is what you make of it, thinking about what possibilities may have opened up by you having more time. It can be whatever you want it to be.
Now, all that possible positive spin I've said aside, if you really are monogamous at heart, and your wife really is poly at heart, and part of what you need in your relationship is for HER to be monogamous too, then all the advice in the world won't help. BUT - if you could learn to live with (and maybe even enjoy) her being poly and you having more time to pursue your own activities, then it could work out.