It looks as if the project needs a reboot.
I was thinking something along the lines of this. What I was imagining was forming an entirely new team and starting somewhat fresh. We'd still use the same code and assets and story, but we'd brainstorm about what kind of game we want to build with it. I thought of this because its hard to be enthusiastic about joining a project that pretty much has most of the core mechanics and gameplay nailed down that were decided by a group of people years ago who have long since parted ways with this project. So I've been wondering if I could roll with that sort of mindset, attract a new team of enthusiastic people and share what we have to work with, and see where we want to go from there.
You're the programmer, right? I'd do the reverse: Keep the gameplay and code, scrap the assets and story. Recruit artists and musicians and map makers to use the Allacrost engine to make something new.
If you're going to recruit new artists, they'll have more fun deciding (collectively) on their own art style, instead of trying to make new art for someone else's art style. The art may go in a style direction you personally aren't as interested in, but that's the cost of holding their attention. By presenting the existing art assets, but giving them the permission to them or ignore them, they may end up salvaging some of it anyway. By "art style", I don't mean the artists get the dictate when/where the story takes place (future, past, fantasy whatever) - the story dictates that. But free the new artists from the burden of having to be consistent with the old artists art decisions, and give the new artists the freedom to salvage or discard the old art assets.
Same with the music. Same with the map making.
The cost of map makers is either money or letting them work on something they enjoy working on. Ditto for musicians. Ditto for artists (they want to work in the style that interests them). They are willing to bend somewhat, to work on collectively what the new group wants to work on, but they would probably be less interested in working on something that some ancient group from 10 years ago decided on. Try to not be too intrusive in their decision making, but do remind them that it has to fit in with the story and the rest of the sub-groups. You can also steer them subtly by using positive feedback ("That sounds cool!", "That's interesting, could you elaborate on that?"), but avoid negative feedback and let them make decisions you don't necessarily agree with.
Keep the gameplay. Be the lead programmer and lead gameplay mechanic designer. Let others be the lead artist and lead writer and lead composer and lead map maker.
See if you can recruit three to five artists, three to five map makers, and etc.., and let them choose from amongst themselves a lead for each of their sub-groups.
If you no longer need writers, then keep the old story. But if you still need artists, form a new artist sub-group, let the artists choose their own art lead, and let them create a new art direction and art style, even if it means scrapping the existing work. Same with the map makers - collect a new group of 3-5, let them choose their own lead by voting, the lead reports to you, and you act as a director to make sure the sub-groups work together well. Or you can personally choose the leaders, based off of who seems like the best leader - but you should wait until they've been on the team for several months before choosing someone.
When map makers need a piece of art, they should open MS Paint and make the quickest and junkiest piece of art imaginable. Then when that map is actually in-game, the artists would move quickly to replace it, because A) they'd see their results ingame immediately which makes them feel good, B) the improvement to the junk graphics would make everyone feel like progress is being made (including the map maker) making everyone feel good, and C) the artists would be silently steered towards making art that is actually needed and would also be motivated to step up and give it a try, because anything they make would be better than the MS Paint scrawling (they'd have more confidence to try, because "anything I make would be better than that").
By default, you are the "lead" of every subgroup until the subgroup gets large enough to need its own leader. This should be at least three people. Any leader should've already been on the project for at least 90 days and should be able to commit at least 10 hours a week. The sub-group leader (once appointed by you or elected or whatever), should also be responsible for recruiting more members for his own sub-group (and help recruit for the project as a whole). Team members can be on multiple subgroups (art and map making, for example).
Setup a roadmap with milestones. 2 1/2 years (30 months). Try to hit the goals. But even if they are missed, it'll still give people a target to shoot for and make the project not seem endless.
Just some thoughts from an inexperienced gent. I've worked on one non-commercial team project before that dragged on for four years (I wasn't the project leader, but I was the lead artist, scripter, and map maker), but that's about it. I'm currently working on a commercial solo project that's been going on for almost five years now - and though I have some family and friends contributing art and music and map making, it's mostly me doing 99% of the work (by choice), though I am making-requests/placing-orders about what I want when I need it, so I don't consider it to be a team project because it requires pretty much zero team management (at least at this stage), so I don't have any experience leading a project as large a scope or as long a duration as yours.
