I also have noticed a significant reduction in battery life recently. I updated to Android 11, hoping it would fix things. The same, if not worse. I have 100s of apps I use, and don't have the mental bandwidth to put the phone in Safe Mode to isolate who is doing what. I glance at my battery stats from time to time, and nothing stands out. I have turned off live wallpaper, don't allow searching for WiFi-Bluetooth even when but using it, screen a dim as I can stand it, etc. But still, battery life horrible.
After the Android 11 update, and still having battery issues, I performed a factory reset. That process took about 8 hours. I still forgot to log into Chrome to backup all my Bookmarks!!
I am hoping my 2 year old phone battery has not physically diminished this significantly. But, alas, this just may be the reason. I don't see myself having the phone taken apart to replace the battery.