Thats right, reddit is removing its horrible implementation of custom emojis, in its ever ongoing journey to lose all feature advantages it has over lemmy. Now we only need them to remove post tags and user flairs, and lemmy will be superior in every single way.
They are really deadset on removing every single community customisation out there!
What they can (should) do is support lemmy’s api, so you can use lemmy apps with it.
The language something is written in usually doesn’t matter much, database stuff and i/o are the main performance bottleneck. Instagram and threads serve a massive amount of people and they’re written in python.