I know how to fix Poppy
It seems a lot of people are finding Poppy lackluster right now, and her ult is far too situational to be of good use, both instant and channeled. Not to mention, she has a really one dimensional playstyle.
So, I have a solution to the problem. I've noticed that during most fights, to not disrupt them, I hardly use Poppy's joke of an ult. So I figured, this is a good opportunity to retool her kit. I call it the "Stance Change." Similar to Jayce, using her ult/ fourth skill should change her weapons/ capabilities. For Poppy, she should have an _offensive _and _defensive _stance change.
In her offensive state, it can be similar to what she is now with her abilities. Her hammer is her main attack mode. To emphasize this, her W should be split between both modes. In offensive, you can likely give her the movespeed buff and the dash denial. Or you can take it away so her power budget allows her to still retain her passive. The passive is the important part and I'll mention it in the defensive section. The charge can remain as normal, as well. The key to these is that her damage ratios should be higher in this mode, so people who want to build offensive can get a return on it. You can compensate by having her have lower armor and mr buffs from her W than normal.
Then defensive mode should be the reverse. Bonus AD (if any), but have her cc last longer. The Q's slow will be better or it can have some other cc effect to show it as a reliable defensive ability. Her W will lose its movespeed buff, but gets an increased active of the dash denial, along with her armor and mr being higher. In this mode, her shield is "out" so should be her reasoning for being defensively tougher. Her charge can still remain, too, but it should also have someway to decrease the enemies's resistances so she isn't just a one-off utility user.
If you want, you can even move the armor and mr buffs to her passive so it changes depending on what stance she is in. Her passive right now is very mediocre compared to the utility of something more consistent to her playstyle.
That's just my suggestion.