It’s true that Android 5.0 Lollipop isn’t the best version for Galaxy Note 3.
But after receiving the recent update(Security patch & various bug fixes),
I must say that the device is performing much better than then.
I also hated Lollipop back then but after receiving the recent update I realized that the issues have been solved up to some extent. Having considering the new features which Lollipop has, I’d rater stay with Lollipop than downgrading my Note3 to KitKat.