Hi there,
I figured I'd take a stab at some of your points here, since it's an interesting discussion, and you're clearly very passionate about it:
Hidden Power ->
Hidden Power is more along the lines of Taric's Shatter passive, Sona's old Q/W/E auras, Soraka's old passive, etc. It's stuff with zero gameplay, zero thought put into it, just purely power without gameplay. In fact, the thing we have issue with is "Power without Gameplay," less so "Invisible Power." They're fairly similar concepts, but PWG is more concrete.
As a jungler, I make a conscious choice with my Smites. Players choose which camps to start at based upon the Smite rewards. There's gameplay with every single jungle Smite buff gained. And in fact, only one of them has meaningful impact with even a chance of being invisible (Gromp--the vision-related stuff is pretty clean in execution), and the rest is just extra meaningful decisions and gameplay for a jungler as they navigate the jungle.
There is no Armor/MR buff for the defending team. That never went live.
The Challenging Smite damage debuff is somewhat bundled in, that's true. You'd have to talk to a game designer about that one.
Snowballing is bad ->
That's not really what we're saying. Our thrust is that a winning team should feel like they're winning and feel like they're making meaningful progress, but at the same time, the losing team should feel like they have ways to get back into the game. See, here's the thing about the new Dragon mechanic: The first buff is pretty good. Still, it's worth less in gold value than the gold of the old first Dragon. At any point during the game, the losing team can manage to claim one Dragon and gain that one really important buff for bonus AD/AP. The Dragon's only better than Baron if you managed to get FIVE of them (over a 30 minute span), without your opponent stealing any of them away from you (Add 6 minutes if that's the case). That's pretty damn fair. You get 30 minutes to try to stop Dragon control before the "Better than Baron" snowball.
Games have to snowball to a certain extent, otherwise nothing matters and the game is just a coinflip in the end. Rather, we want to have a healthy amount of snowballing. There should be ways to come back, but building a lead should feel meaningful.
Flat Armor/Magic Pen ->
Sure, it's still a problematic stat. But just because we've prioritized other things above that work and changes to it aren't ready yet, how is that hypocritical? It's not like we were like "Yo dawg, let's add a bunch more flat pen items!" Okay, yes I realize we put Brutalizer into the AD Jungle Enchantment, but that's still only coming in for a single champion (if that) each game.
Enforcing the Meta ->
Really nothing we've done enforces a requirement in how you play the game. We've seen people bring Smite and still head top lane because they want the Smite benefits and items. I wouldn't be surprised if a 5-Smite all lane team were totally viable, since the jungle respawns so slowly now. It's actually probably increased the ability for teams to run no jungler. Yes, the value of Dragon/Baron make bringing Smite into the game really valuable, but the way you do it is still up to the players and teams. And if we've so severely pushed champions into "only being able to support others" why is solo lane Lulu/Karma/Zilean/etc. still a thing? Some champions are TRUE protectors (Sona, Soraka for example) and so they naturally don't fit well in solo lanes, but that's no different from saying, "Well, Annie's a bad Marksman, way to enforce the meta, Riot." Champions are good at different things. This is a GOOD thing. Otherwise, picking a champion is literally irrelevant.
Counterplay ->
First, item-based counterplay is not very interesting. One of the designers posted about Tenacity and Knockups a few days ago, if you want to look around for that.
Second, the thing is we've actually been INCREASING ability counterplay of the course of the game. On launch, what percentage of champions had point and click stuns? Literally, just put your cursor over someone, receive stun, no extra cost to you. Off the top of my head, I can think of Taric, Annie, Sion. You could make a case for Ryze... I can't think of any more right now. Almost 10% of the champion lineup had a literally zero-counterplay hard crowd control. Since then we've removed Sion's and added a whole bunch of other champions, lowering that percentage pretty severely. What, 2% now? Any champion that DID get targeted CC had some kind of drawback: Nocturne has to hold the tether. Malzahar has to safely channel. Vi is now inside the team and better be tanky enough to survive. Otherwise, every hard CC we add to the game can be dodged or has some kind of extra counter-playable requirement in order to receive the CC.
As for Kalista, it's not something I have the vocabulary or knowledge to talk about, so again, best saved for one of our game designers or CertainlyT himself.
Finally, there's one more thing I want to bring up: Design is all about achieving a balance, about give and take. That's why finding an appropriate amount of snowballing is important. You can basically slide how much a lead matters up or down. Having too much or too litter are both really bad. You get the right amount. If you wanted 100% counterplay to everything you'd give everyone perfect vision of the map and no crowd control, because how can you counter-play when you can't move? Well, there's reasons to have CC. There's reasons to have some champions with more mobility than others. There's reasons and benefits (and drawbacks) to every decision you make in game design. It's about maximizing fun versus frustration.
<---still without substantial nerfs. Then they release 
