I've been playing this for a few days.
As a fighting game fan, it's easy to get into, not terribly deep but fun. I can already see some balance issues early on with some characters' Ultras being overpowered (Kateryn) but it could be that my character isn't terribly strong.
The problem I see is that it's not a deep game so people who like fighting games may not find much to keep them busy, but people who don't play fighters may find it difficult and give up early complaining that it's pay to win (which it's not.) Still, for a free game, it's not bad. You can unlock higher tier characters with a lot of grinding, but I suppose that's to be expected.