I don't know what the sub-genre is calling itself, but there's been a recent trend of games which are mostly PvP, you build a card deck and then battle it out. The one I played most recently was called Siege Titans or something like that, and the biggest one is probably Clash Royale.
Anyway, this is the South Park version, and I'm having a blast. The core game concepts are similar to those other games, you build your deck and cast spells or summon help in a battle, with 3 blocks to fall before you win or lose. In this case, the battle is a side scrolling affair. You level up by upgrading your cards, similar to other games in this genre. A subtle difference is that you need to collect specific materials for some of the upgrades, and then every few levels you'll need to have X number of the same card to do the next upgrade.
Two big differences give this game an edge over the others for me. One of course is the South Park license. The animations and voiceovers are all tons of fun, and they've done a great job creating different themed versions of all the characters with different AI, powers and effectiveness. It's pretty hilarious at the getgo but soon enough it becomes a fairly strategic affair. Timing and combining the right cards, protecting your main guy while attacking the other guys, all becomes a fair challenge.
Then the really big difference. There's a full-fledged PvE game to play/follow as well. At first I thought it was just a tutorial, but it's actually a big part of the game. It's not completely independent, because at the end of each section you are forced to win 3 PvP battles before you can progress to the next section. Some people may not like that, but the good news is you can (and should) go back and replay older missions for better rewards. This really sets it apart from some of the other games in this genre, because you can pick and choose which maps to "farm" depending on which cards you want to upgrade. Each map can be played 15 times (I think), but the difficulty ramps up each time you complete it (as do the rewards). PvE plays out differently from PvP because enemies can come from either side of you as you walk/scroll, whereas in PvP you are always facing each other and going after the others' leader.
Yes, the game is freemium and yes, there's a P2W aspect in that you can of course spend money to just buy tons of upgrades/cards, but I think the PvE portion helps greatly to negate it. And like other games, they give you free card packs every 4 hours to open. I spent some real money on the game before I realized how useful the PvE aspect was, but I don't mind supporting the game as I really enjoy it.
In the end, even though I haven't watched the show as much as I used to, there's something just incredibly fun watching Astronaut Butters attack Sheriff Cartman with his helmet, or bask in the cuteness of splitting Gizmo Ike into two.