Well, we saw this trend from the start of Diamond and Pearl. PCL started making cards more and more broken with the release of each new set.
I really must agree, I miss the days of RS-on and HL-on that involved steady, slow-paced, setup decks, with those 1 or 2 speed decks that could also do fairly well.
I dunno what happened, but this whole SP nonsense has turned the game around completely. Now everything must setup within turn 1-2 or else you essentially lose. And due to SP pokemon all being basic, they are naturally fast, and PCL has to create cards like BTS just so that setup decks can compete.
I think what happened was PCL wanted increased diversity in deck choice, to where kids could choose their favorite Pokemon to base a deck on and still be able to make it slightly competitive, but by doing this they also increased the donk factor in the game, and made the game much more speed based.
The game is still thriving though. We have seen amazing growth. And with a larger player base comes more complaining, and increased problems. AND, I do believe that there is a healthy future for the game. Yes, we will have to embrace this fast paced environment BUT in the next couple sets we are going to see cards like Spiritomb which will help slow the game down to a manageable state.
I dunno, next format will be the first format we have ever had where there is literally NO rotation of sets. I know I am personally a little scared. We will see how it goes though.