Like Pollywanna said, it's all about character choice to build an effective team, and keeping those characters leveled up. The former is what makes the game fun, the latter is what got in the way of me enjoying it a lot of time (once the grinding got ridiculous). If it weren't for the grinding (and typical F2P model shenanigans - daily login bonuses, microtransactions, etc... and of course the grinding is part of that; to encourage you to buy stuff to make it faster)... I would have easily recommended this game. Certainly a faaaaar better take on this gameplay than Minifigures Online (which it shares many elements with, but does 10x better).
There's actually quite a bit of strategy in choosing an effective combo of minifigures to go up against the enemies in the level - my playthrough cut out all the failed attempts with flawed teams, for the sake of time.
Besides this...
... there's also Magic and Physical character/damage/resistance types, character classes (attacker/defender/supporter), you can alter those stats with Enhance Bricks (which in and of itself requires some knowhow of how to squeeze the most out of them), and a bunch of status effects like Poison (health drains over time), Freeze (character is frozen in ice and is a sitting duck, can't do anything), Petrify (like freeze but even more brutal), Blind (all the character's attacks miss), Mind Control (character starts attacking others on its own side), etc. Your heroes can both inflict these status effects on enemies, and resist them under certain conditions or probabilities (which, again, can and need to be altered or leveled up).
So you've gotta make a team taking all of that into account, and unless you're several levels ahead of the AI, you still need to be fairly smart in how you play and use character's skills to survive (and complete the level under the time limit).
If anything, I thought it was surprisingly complex for a game presumably aimed at kids.
Because doing damage isn't its main function. It freezes enemies, which can be extremely useful if built at the right time, or a total waste if built too early or late.
The twist of this boss fight is you have to lure it into specific locations to make it vulnerable to damage (see also: the time limit... and choosing a character combo that can do damage quickly enough, but still be capable of healing [only supporters have heailing abilities and they don't do much damage] while also countering the boss's effects). It was a good challenge, one of the better ones in the game. You sure like ranting about things you haven't played and have only gotten a vague idea of how they work from watching videos, lol... There's things in this game to rant about but none of them are what you're saying.