He is just a strong early mid champ that os irrelevant in late game. Ok the whole rework was good but look at irelia or akali rework, these champs became broken, but pantheon will be forgotten in 2 weeks
He changed and is almost perfect tbh. He is not as oppressive as he once was. They only think that is wrong with him is he still has a point and click stun that is also a leap.
No, he got worse in the damage department.
I just don't see a reason to play him over 
tbh. Aatrox has a better early game, scales way better into late, and can carry harder. 
scaling needs to be increased across the board
he'll be forgotten at lower ranks because folks just outright can't play him lol. need to know how to stack his passive and use his E and R correctly which just won't happen in most mmr's.
He became a much better duelist, is still pretty good at bullying lanes, and got waveclear meaning he can mid lane pretty successfully (also hard counters Yasuo, which is always a big plus). Hard to get a exact idea on balance in a day, but I personally think he has a lot of potential. Nothing screams "broken" but he has a lot more options as a champion now.
I just had a 1/4/5 Top lane Panth with less than a hundred CS and a black cleaver and a corrupting potion solo baron. No recalls and when we found him just seconds after killing the thing, he was already at full hp.
I mean did you WANT another Irelia?
Honestly I'm not sure much has changed with this rework in the grand scheme of things. He used to be a braindead easy laner that turned into a beefy stunbot the longer the game went. Now he takes a bit more effort but gained a lot of range on his Q and is still pretty oppressive, and of course his new block which helps his late a bit compared to old panth. but still he just transitions into a beefy stunbot.
He is a sexist
Not really. He has more tools now like the E shield even if it really does feel like a glorified Zhonya's most of the time.
He is just worse
