I agree that a game with entirely 5-5 match-ups is the goal, but... I mean, look at every single competitive game, and every single fighting game ever made, even those where that was an explicit design goal. I doubt any of them, judged by that criteria, could be said to have succeeded. It turns out it is extremely hard to get that kind of balance. If you further add the criteria "and in all those 5-5 match-ups, each player has to do the same amount of work for it to be even" I doubt any asymmetrical game with a roster bigger than 2 can say it has achieved that goal.
I still agree with you that it is a goal that should be top of mind for game designers. If anyone is passionately in pursuit of that goal, I would say it is the designers of this game. Just... you know... it turns out it's impossibly hard.
The other thing to keep in mind is, depending on your experience with the game, balance criticism can be more or less about inexperience than about balance. Fantasy Strike is very accessible, but that accessibility belies its skill ceiling. There are real differences between a player who has just picked up a controller, a player who has been playing for 10 hours, a player that has been playing for 100 hours, etc.
I get frustrated with the game too. There are moments where, playing as Rook, I feel absolutely helpless to win against an opponent that does "X thing" over and over again. When that happens, and I feel like I've tried everything that I can, I try not to immediately go to "X thing" is busted. (Note: I try. I don't always succeed!) I'll go to the forums or discord first, and I'll see if anyone has any suggestions. I'll see if there's some way to play that avoids my opponent being in a position to do "X thing" to me in the first place. I'll ask more experienced players what they think about "X thing" and what I should do to beat it.
I hope this doesn't come across as "don't complain." At the end of the day, this is not the finished game. Balance tweaks should absolutely be on the table. And they are! Heck, with the throw button change, entire systems changes are on the table right now! But if it seems like a complaint comes down to inexperience, the best approach should be to try and share information.