No one is arguing that FB has a huge amount of content, renders and animations, but where did you get those numbers from? I'm looking at my Ep2 v16 and Ep3 v16 folders and this is what I get:
Ep2 v16 - the total size of the unpacked game = 10.2 Gb (excluding the folder "saves"), the folder with renders (even if you do not separate such things as overlay images, backgrounds, etc.) total = 27422 images with a total weight of 8.12 Gb Folder with animations (849 pieces) weighs about 1.9Gb
Ep3 v16 - the total size of the unpacked game ~ 16,4 Gb (excluding the folder "saves"), folder with renders (all, without division into types) - 37567 renders size = 11,8 Gb, folder with animations (804 pieces) and 4,30 Gb.
DM intelligently split the game into parts when necessary, so that the imperfect RenPy could cope with such large amounts of data. So the game is still gigantic in terms of content (renders and animation), but still not such a monster as you write.