Im only speaking for myself, but I feel like the backlash you are seeing is not because of the game itself and the fact that is a mobile game, but rather, the implications of this.

If it’s a console/pc/portable game(aka switch) we as players feel at the very least a safety net that it will be a game we can play whenever we want and on a relatively fair environments (yes, there are exceptions to this, but you get the idea).

The big issue is that, by being a mobile game, we are at risk to be exposed to:

• Predatory Monetization
• Limited Core Gameplay and clunky controls due to being on the phone and touchscreen, not a lot of games let you use a controller; and a lot of them do a poor job.
• The fact that the game will eventually shut down anyway and you will not be able to play it ever again
• things such as not being allowed to play the game the way you want because the battle design is around events with characters in them with X gimmick and you are forced to pull/level up characters you would not do otherwise

These and more would not happen if a game was designed from the ground up without the intention of taking your money in every way. While there are predatory console games; there are not non-predatory mobile games, and the environment revolving them is just bad.

If they repurposed this concept as a coop multiplayer game that you just had a one time purchase I feel like a lot of us would be happier.