I would have agreed 4 years ago, but idk about now. They've been increasingly "Oppo-fied" and I'm having more issues with my 8 Pro now on A14 than I did on A11. Camera apps not working, different keyboard issues, constant Bluetooth disconnects, apps opening and then insta-closing. It's frustrating AF.
Edit- Android 14 is still in beta so that's a very poor example.
It's also possible your phone is simply defect, do you have confirmation others have similar problems?
Is that an official update from One Plus? Because that's more than 3 years old model, and usually they only give 2-3 updates, meaning it should end with Android 12 or 13.
Edit: It can't be official since the phone is 3+ years old, and Android 14 is in beta.
Most phone manufactures create their own version of Android. Usually they are pretty full of useless junk and a ton of UI changes. By saying "mostly Android" you're urually saying "mostly [original] Android".