CreateStudio Animation Made Easy - CreateStudio
Tool for creating 2D and 3D animated videos. The basic plan is $99 for a lifetime license, with limited characters and templates.
Free Lottie Animation Files, Tools & Plugins - LottieFiles
Lottie animations are lightweight. This site has both free and paid animations. You can also do quick edits in their browser-based editor (like changing colors or text), as well as integrating with other tools. The animations users see after completing a Duolingo lesson are Lottie animations.