Longtime writer here who has always been very fandom specific.
I think Saiya says it best. So I've come to approach Fandom stuff with an open mind and try to compromise where I can. Much like you, I'm more CanonXCanon and always have been. I try to let people still have the freedom to tell me what "Their" version of say Lois Lane or Mary Jane are, but I still would like it to be as close to the canon and not an extreme take.
However, you're always going to have trouble with any fandom because some people feel like it's stealing another persons work and or character (especially if we're talking canon characters). Then there's also the question of how well they know the character and if they feel they can play them true to that character. There's a lot of unknowns and potential brick walls in there that turn people off.
But to go back to your original question about making it more appealing (the above is just kind of my random thoughts on the matter), if you want to make it more appealing I think the best thing you can do is just promote the idea that you're open to ideas, compromise where you can, and be firm where you can't compromise. Also (and this isn't to be rude or come off as such) accept that you might be waiting a long time for your bolt of lightning perfect match up OR you might not get a specific pairing you want or canon you want. It sucks but I think we've all been there with that one eye in the sky idea we always wanted to do but no one else wanted to do.
Hope I helped! I've been writing Fandom Canon stuff since I first picked up a pencil and started this lovely craft and there are always highs and lows with it. Keep the optimism/positivity up!