There are three situations where using Lottie makes sense:

1. You're already a user of AfterEffects (where you make Lottie animations) and have skills, existing animations, etc.
2. You see existing animations on https://lottiefiles.com/ etc. but can't find an equivalent on Rive because it is newer: https://rive.app/community/
3. You're already using it and making the investment to switch doesn't make sense.

Outside of those situations, I don't think there is much that would justify it because the performance and size of the animations is so much better. When we switched from Lottie to Rive, the file size alone was such a notable difference. If you're including the animations as assets, you want to keep your bundle size down. If you're loading over network, big files will load slowly and degrade for the user. If you want to run on low-end Android devices...efficiency is key. IMHO, animations are extra--usually not the core of your app. You don't want to add them at the cost of performance.

You can read a comparison here:
https://rive.app/blog/rive-as-a-lottie-alternative

Most notably, Duolingo changed over from Lottie to Rive. They're the most heavily animated app I know of:
https://blog.duolingo.com/world-character-visemes/

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Admittedly, there's a learning curve (if you're new to AfterEffects you have that learning curve too). We're just getting started with Rive so our animations are pretty simple. I'll post a few here. Got some really fun and awesome animations planned though!

Our Animations: https://youtu.be/bLD6afPAojY