kycunt and I abused it by letting the battery run totally dead for months.
Well you didn't mention this before. Had you said this, i'd have explained to you that that's a sure way to kill a healthy battery. Batteries that run dry and are kept that way rarely recover.
The most ideal way to store a battery is to have it at 50% and store in cool environment. This is exactly how you receive brand new phones and laptops. They are always this way because its been tested and proven.
But I'd say dont give up on the phone. The pixel 5 is quite a good phone and frankly i prefer it to pixel 6. See if you can get it repaired at a fair price and from a trustworthy repairer.
Read this thread for the last word on batteries.