LOL. Please. What tools, other than flash, were animators using to make videos for the web back then? Remember that they can’t be saved as videos since video streaming hadn’t come into its own and video file sizes were too large for our Asian retailers. The nice thing about flash animations is they were vector graphics. Super small file sizes.
This is outside my expertise but i remember doing svg animations, web gl animations and unity animations roughly ~10 years ago.
But maybe that was a few years to late or not applicable to your case?
But an app with vector animations should have been doable (not to hard in theory) if you could have found the investment for it, right?
Professional animators are artists. They need professional animation tools, like flash, to work with, not svg/webgl/unity that a programmer would be more comfortable with. They need things like a timeline, character library, animation pallet, built in tweening tools, etc.
(Unity do have animations tools for artists (it is partly made for artists) but not so good for vector graphics and not close to flash, and definitely not back then.)