I must confess I'd never heard of "trunk novels" before coming to this forum, and the concept puzzled me and still does. I rarely consider any story COMPLETELY abandoned, and IMO almost anything can be fixed, if one has the drive to fix it. I find the advice above to "Don't dare try it!--work on something more promising!" perplexing as well. What if the OP really DOES have it in them to make this story work? Isn't that worth trying? You'd advise against it just because it didn't work for you personally? It seems such a shame and a waste for somebody who really loves their story to be told not to bother with it because it's a waste of time and effort.

Since the OP is even asking and thinking about this, I think that's a good sign in itself that it could work.
I started a novel series back in high school and such and got three of them written. They were good to me at the time but following a royal lambasting by a self-professed "critic" (read: troll) online some years ago, I lost all faith in them and "trunked" them, if you will. But the part of me that never lets stories go is fortunately always on somewhere. I recently started rewriting the first of them. It's stalled out, but not because it's going lousy, more like just my trouble with any writing lately. I think the rewrite was going really well and hope to get back to it sometime soon. I believe in these stories. They're really, really lousily written, yes. But if I believe in them enough I can fix them. It just takes time and work.
And yes, I do have stories that I've decided I should not spend my time and effort on right now, so I can dedicate that time and effort to things that are more promising. But I would never tell somebody outright to just trash something because there might be more promising things to work on. Especially if they're excited at the prospect of revamping a story with potential. Say the OP decides not to redo the trunked novel based on this advice. Who's to say the new story they start in its place won't turn out to be trunkworthy material, too...? We really can't know until we try.
Maybe a "better, more promising thing" for this writer would be to redo this story.
That's really all I can say. If you love and believe in a story enough, you can fix it.
That is my opinion based on my personal experience and I shan't defend it, so take it or leave it.
Good luck with your novel. I say go for it.
