IIRC many 2D animators considered the old Adobe Flash Professional to be one of the best 2D animation tools ever made.
https://en.wikipedia.org/wiki/My_Little_Pony:_Friendship_Is_...
https://en.wikipedia.org/wiki/List_of_Flash_animated_televis...
One of my roommates in the heyday of Flash was an industrial designer who was paid by an Italian business to design aftermarket wheels for cars, which he did in Flash. Eventually he figured out a Flash > Studio Max workflow he liked and finished projects in 3D that way.
That guy could draw anything in Flash and preferred it over Illustrator, Photoshop, and Fireworks.
Jonathan Gay pivoted it to animation shortly thereafter and rebranded it as FutureSplash, and then got bought out by Macromedia.