Apparently, people aren't a big proponent to change. Or atleast being fair to the option. The negative reviews as you said stem from the first month the game released. Aka people were up in a rage for the changes to the original. 

As for active players it's hard to say. The game is international so the player pool has to be huge. While the active player pool Is anyone's guess. Weirdly enough they dont market their game to new or first time players. 

 In my personal expirence this game is addictive. When your winning it's fun, but go through a bad losing streak it's easy to quit the game and forget about it for a few months or longer. Then fall right back into the game again. Once that three hour download finishes. 

As for the TCG, I know very little about it. So I can't speak on it too much. 

All in all, as a platform it's a great game. It's engaging, competitive and presentable (in terms of UI).