Like another comment said, an animatic is certainly more feasible. You'd be looking at a few thousand drawings for a two hour animatic instead of hundreds of thousands of drawings for a two hour animation. Even so, it may be more possible for several artists to each tackle a couple scenes, rather than getting one artist to do the whole thing. If you have ever seen the Hamilton musical fan animatic, that's what they did - but for them, it was a labor of love. I still believe you will not have much or any luck finding someone to complete a full-length movie as an animatic for you for free.
If you're just trying to have some kind of audio visual media to attach to your script, you don't have to do the entire movie. In fact, if you pitch the entire movie to a studio, they might wonder why they should even bother making the movie if you already did it. And I guarantee that nobody in acquisitions at any studio will sit and watch a two hour animatic when they're poring through piles of submissions.
Instead, maybe consider making a five-minute animatic that is just one key scene from your script that captures the vibe of your story. Like a mini pilot. Not only is it a much more achievable goal for both you and a potential artist, but it's also far more likely to actually be watched by a member of an acquisitions team.
