Fist this post is based on the reveal blog post, I'm not on PTR.
Second I'm not a Poppy main mostly played her on dominion or aram, but almost every game was fun and full of epic plays and fails.
So old Poppy is probably the only champ in LOL with no AOE skill. She is a single target high dmg assasin and an exceptional duelist, probably the best tower diver in the game, and generaly one of the most aggressive (if not the most aggressive) champ in the game. She has no wave clear and a bad lane phase but a late game hyper carry.
Yes her ulti was bad, but there was a few ways it could be changed. i.e.:
1. reduce its defense by turning into a reduce dmg or reduce cc duration or both.
2. make it a single target assassin skill by reduced or no dmg against the other enemy champs or make it instantly end if Poppy use a skill or aa on another enemy.
She has a short but unique ambassador based lore with cool diplomacy related skill names and a bad-ass look.
- Q single target dmg nerfed in most situation for a area effect so small that you wont be able to hit more then 3 minion with it and anyone can avoid the second dmg unless stunned or rooted.
- W removed ramp up effect and dmg, added mr (witch is mostly useless in the ad top meta) and anti dash effect turns an aggressive skill into a defensive skill.
- E seams to be the same
- A full utility ulti with limited dmg and practically only good for saving both yourself and the enemy champ (from your arriving teammates or your turret) in a 1v1 situation. And a channeling skill that can be interrupted.
Passive: change a reliable defensive passive to this. The occasion ranged aa is nice, but linking the shield to aa means you cant hold it until you need it and its unreliable even when not on cd because you need a last hit or pick up the buckler to activate it. It can be still useful on even op on lane (based on the cd) but it is potentially useless in a big teamfight because: 1. you wont be last hitting anything, 2 you either sticking to the enemy carries or protecting your own carries so you cant afford to run after you buckler 3. you are surrounded by enemy champs who can step on the buckler even without trying.
And I thought tanks should be their best in the teamfigths.
So they nerfed defensive skills and practically force a tank build to stay alive in the full melee range she has, then nerfed her dmg just to be sure.
So high dmg turned into low dmg, aggressive into a defensive peal tank (not even a juggernaut), and a duelist into its opposite that good when there are other champs from both team. She can tower dive, but only like the other cc tanks taking turret aggro and cc-ing the target for the carries and not the go in take out the champ the assassin way like the old Poppy.
At least thanks to the limitations of the new passive and the lack of sustain almost any champ with a longer ranged ability or aa then Poppy (so almost everyone) can harass her easily. This, the removed dmg on the W and the microscopic aoe on the q most likely means she will be still crap early game :).
And the worst of it is that compared to the tanks with similar kit like Sejuani or Gragas she is not that good either. Her dash with cc can't be used to escape or wall jump in most cases, and the cc is not sure. Her area of slow is smallest and in melee range. They have % dmg too, and even thou her cc ulti remove enemy champs from the fight for the longest time, their ulti is instant not channeled, has much bigger aoe, can be used to lock down and kill a lone enemy and generally at least as good if not better in most situation.
So after they changed her identity gameplay wise to the opposite (short of making her a ranged mage or marksman), RITO not doing half work erases her existing lore and give her a new one, than change her looks as the finishing touch. (Personal opinion: Both the cute look instead of the bad-ass one, and the "I'm looking for my hero to give my magic hammer to, because I'm too stupid and insecure to realize that I'm worthy of wielding it." story is a change into a bad direction).
Practically they removed Poppy from the game then took the name and the hammer wielding yordle look and gave it to a completely new champ. At least I hope they wont release it with the usual "... while keep her/his identity as a ..." line in the patch notes.