itch.io

My bad, I'm tired. You said so right in the title. Barring more specific issues, it's probably just that mobile devices are a lot weaker than a PC. The raw specs are deceiving. So you probably just need to optimize your game a lot.

Well first problem is Unity will eat lots of ram from devices, there is no way to fix this, all Unity games suffer from it thus the bad reputation of unity comes from it. Next is your models are way to high definition , you dont need the best models, you need the visuals. My recommendation is ditch Unity if you want to upload this on HTML with the 3D models and use   https://www.babylonjs.com/

I would also made the models have less polygons so people wont have to wait 5 mins for it to load.

Really cool models of the skull and brain!

I'm assuming your game is rendering these on the fly. Because they're so detailed, yeah that polygon count is going to kill your performance.

Since your game is basically just showing animations, I would just create and play those instead of trying to have Unity move the objects/camera and render lighting in real-time.

For example, if  I make a GIF of just this scene:

This short GIF clip is only 446k.  The Mp4 version was only 130k.