It's time to dumpster this champion into garbage tier until his rework. He has no gameplay whatsoever and he does not fall off until very late game. He's maintained a 54% winrate and 7-9% pickrate for the last 6 months. It has nothing to do with picks or counterpicks, pantheon has been OP for a long time and he shouldn't be allowed to even exist because he offers no meaningful counterplay to his opponents.
The bronze and silver lords on this board are going to white knight him and use the same old tired ass, worn out arguments of "just don't cs for the first 30 minutes, he falls off, just counterpick him, just gank him, just don't play the game when he's picked." I beg of you to disregard it, people have realized he's been a problem for a long time and riot has done nothing about it. It's time to do something about it.