There's a difference between healthy counterPLAY and just a flat out counter.
You shouldn't win lane / teamfight / whatever just because you chose a champion that happens to 'counter' my champion. It can give you an advantage, sure. Outright making the less skilled player have a considerably higher chance of winning though? No thanks.
As per my original point - just as Yasuo invalidates a lot of champions, it seems Poppy will do the same. I don't like champions that outright invalidate other choices if you don't ban them. Every champion should strictly ADD variety to the game. If introducing a champion removes the viability of 2 or more champions, it's SUBTRACTING variety from the game. It further enforces what champions are reasonable picks and what ones will never see the light of day.
Take any champion that's based around sustained damage, or a champion based around CC and innate tankiness, or a champion that's based around mobility and burst, etc... and all it takes is numerical tweaks to keep them in line and healthy.
Take a champion that PREVENTS another champion from making some action that not all champions have access to (which is to say, stripping your opponent of part of their identity), and that's not healthy. It can't be balanced with numerical tweaks. It will result in one of three states:
A champion select game of rock paper scissors, where the winner is predetermined before anyone actually steps on the rift
The champion being so weak it's never played (like old poppy)
The champion being so strong it's a permanent ban.
There's no healthy alternative. At least that's my view for now. As I said, maybe we'll adapt to it and rely less on dashes and it will be integrated as a core part of the game - but even if it is players are going to complain about it for ages like they do about Yasuo. Maybe Riot will take a suggestion and give the denial a delay, or make it some sort of skillshot or stacking mechanism or anything that has counterplay. I hope so - I'm not counting on it though.