It's all too easy for applications to grow bloated after years of updates. While extra functionality isn't usually harmful, weighing an app down with useless features defeats the whole purpose if it's designed with performance in mind. Firefox Lite was intended to be a stripped-down version for select markets, but as of June 30, Mozilla has stopped supporting it.
Firefox Lite kicked off its life with an entirely different name: Firefox Rocket. Designed specifically for Indonesia, Rocket was released in 2017 with a focus on running fast while minimizing data usage. A year later, Mozilla changed its name to Firefox Lite to better explain the app's goal (although it flip-flopped back and forth a few additional times until its 2.0 update).
Unfortunately, by 2020, Mozilla's lightweight browser was quickly becoming a bloated mess. Firefox Lite came under fire (no pun intended) with its users for adding advertisements throughout both notifications and the New Tab page. Last February, it added a new travel feature that, even if it had been good (it wasn't), would've been rendered useless about a month later anyway. Ultimately, there wasn't much reason to continue using Firefox Lite since each update seemed to take away from its purpose.
Mozilla says it's ending development and support for its browser because the redesigned Firefox app is fast enough to render the "Lite" version redundant. While users are free to continue using the app, it won't receive any additional updates, and it can't be re-downloaded from the Play Store. Firefox Lite managed to reach 5 million downloads over its lifespan, half as many as the beta version for the standard browser.
If you were using Lite and you're looking to switch over to the full-fledged browser, you can download it from the link below or grab the latest APK from APK Mirror. Rest in peace, Firefox Lite.