turns out it's not just me, A LOT of people are facing the absurd battery drain, and OnePlus really should take this into notice. Fingers crossed for the next update, but the
EXTREME ONEPLUS BATTERY DRAIN - OnePlus 8 Pro vs OnePlus 8 / OnePlus 7 Pro / OnePlus 7T / OnePlus 7! - YouTube
Battery Drain Fix - 100% working solution
How To Improve Battery Life On OnePlus 7T
OnePlus 7T Pro battery drain on a unknown app? : r/oneplus
How to improve OnePlus 7 Pro battery life | Android Central