First of all, OP, thank you for bringing this up.
As a Poppy main with over 280k mastery points I can tell you that her overall effectiveness has dropped significantly since her recent nerfs. I feel it every time i play her, Particularly the auto reset. That being said, I've played her for so long that I'm very in-tune with her capabilities and limits and don't typically struggle too often with any particular matchup or role. She is a relatively simple champ to play, but definitely has a high skill cap now in order to be really effective.
Pre-nerf i was hovering around 100 S6 ranked games played around 60-65% winrate. Now i'm at 174 S6 ranked games played with 55% winrate. Which is probably very good compared to many other poppy players considering her winrate on champion.gg of 45.72%.
I still think she is one of the best, if not thee best all around tank in the game. Her kit (if mastered) her be effective against almost any champion and brings a load of CC and engage/disengage with her. This is why the pros still like her, even though her damage and ranges have dropped significantly, the utility she provides is still very strong. When you are in premades and can really count on your team, Supertank poppy is a great solution, particularly if you are the only tank.
However, This may be the old poppy in my speaking (hyper carry), but I still like having more damage in my build than the standard "super tank" poppy builds in higher elo. I feel I can really make an impact if I choose my battles well and turn the tides of the game. (particularly in Silver elo where you can't always count on your teammates)
It's not uncommon for me to go Thunderlords with these types of builds and I recommend trying them out!
Standard / Universal build:

or (only if you're really fed) - with 10% CDR runes

If you really want to have fun try
sometime. It actually works very well on her cause you all in with Stun Auto Q and pretty much kill in one combo.
Also, i too like playing her in the jungle (not as much anymore with the auto attack nerf, but still occasionally). I used to run warrior + Iceborn for instant 40% CDR. Worked great, but now that they have buffed Cinderhulk it's not a bad idea to run that instead.