What is the best animation utility for pre-drawn, multi-layered artwork?

I'm hitting the wall trying to get my drawings to animate using Krita.
I am told this is because Krita is better suited for traditional cell-animation / drawing it out line by line as opposed to a fully drawn and layered image?

Also, I preferably want to animate this thing in a tweening fashion as it's mostly vehicles etc. Yet is this possible for non-vector animation?

 

It's been a while since I've messed around with 2D bone animation for Unity but the ones I remember that should still be good: Spine 2D, Dragonbones (external), Puppet2D, AnyPortrait (asset store). There's a few more out there that have slipped my mind.

I know for sure that you can use raster images with Spine 2D since I've tried it but I believe you can use raster images with the rest as well.

 

Thanks, I'm giving Open Toonz a whirl right now, we'll see how that goes I guess...