Eventually came bosses and raids that were genuinely impossible because beating them were locked behind the new cards in the gacha with each release and hoarding gems because really hard to do let alone the rates allowing you to get a card that will actually allow you to do anything higher than a 45 stam and 45 stam eventually became impossible without certain cards in the gacha that forced 1st turn draws so you stood a chance at getting over the 1st turn without getting wiped instantly.
Multiplayer was the most cancerous thing I have ever seen. If you aren't a whale or lucksack and you need to get carried, good luck. You'll spend most of the time Turn 1 playing with AI teammates because they bailed on you after spamming emotes. The people who frequented it the most were especially among the most toxic players.
It was among the most unique gameplay I have seen in a turn based tcg and it unfortunately got to the point to where SE really hated their community and already replaced it with HGSMA, so they really wanted everybody to move to that instead. There was also an MMO that didn't last long either.
They really made this pay 2 play in the end due to the gacha and the way boss mechanics worked. If you wanted to stay f2p, you would need to commit an unhealthy amount of time and energy to stay relevant and if you aren't rerolling on every single new banner, you were playing catch up for months and by the time you catch up, everything you farmed your life away for was irrelevant, useless and replaced, making all that time spent wasted because having help meant finding people nice enough to carry you, which nobody would because of how hardcore the grind was.
This game needed to be shut down the moment they introduced MMR, they milked this game so hard until everybody bailed on it and the whales couldn't afford to keep the server costs going since the playerbase was nonexistent. Corporate greed ruining good things.
But, that's the life of gacha. Having an offline version available is the smartest thing they've done for the game.
The game was great before they release the MMR gacha..jesus...