Look, man, even if you already did a huge chunk of the work like the script, the storyboarding.. there's little to no incentive for taking up this collaboration.
"Being interested" shouldn't be listed because that should be a given if someone takes the offer. Experienced artists like the ones you're looking for with the requirements of "experience in the sequential art field", experience with insert software", "experience with basic coloring", "experience with webcomics", a portfolio with comic pages, the ability to draw from reference and written description.. This is all along the lines of a paid offer!
One could even look at your artstation, and they'd have to wonder, "Well, why can't he just do it himself? He seems experienced enough." Not to mention, it doesn't sound like you have an end goal in mind if the script is still currently being written. This only makes the commitment sound even bigger to make on the hired person's end because of the uncertainty around the length of the project. In an unpaid offer, I think exposure and creative freedoms are the only thing you CAN offer as incentives, but it doesn't sound like you can give either, given how you worded it. It's a lot more to ask for than you think it is, dude. Tell me that you'd honestly work with someone else who's making the same offer.