The game feels really low in fps despite the fps counter's value saying otherwise

It started a couple patches ago, it wasn't like this. While this is kind of hard to explain, but since recently the in-game counter would count the frame rate to a consistent of 80-90 fps for me, but it FEELS like I'm playing with 20 fps, if you get what I mean.

This makes the game quite unenjoyable to play, as it seriously obliterates my experience with the painfully choppy frame rate despite the good value given by the counter.

I don't know what's wrong, but it sure isn't my eyes and brains magically getting "faster" (as in, my biological spec being so high even 80-90 fps feels too "slow") when I play League. Please fix this asap.

Thanks.