In practice most UIs don't have crazy image based animations and can be done with CSS. Lotties might be good for the one off animated GIF style animations, but

In practice most UIs don't have crazy image based animations and can be done with CSS. Lotties might be good for the one off animated GIF style animations, but in that case why not just use the many tools to create SVG animations? Many designers I've worked with get really excited about Lottie animations but I usually just make the animations in CSS since it's more performant and easier to work with. By the way, CSS animations have gotten significantly easier with the @property rule. Simply edit the CSS variable and your animation will update!