It's free. This isn't a moba where you can have 40 characters with low effort. I mean there is a lot icons does wrong, but also a lot it does right.

You can buy all current and future content for a super reasonable price. The game could have just sold for that. This model allows those who don't mind paying up front to at least have more people to play with, but honestly without trying to be an asshole here, why the fuck are gamers so entitled these days? In what plane of existence is it reasonable to expect all the countless hours of development to just give everything away for free?

Yes, they definitely need more characters and 7 is a rough start, but you can keep playing to earn the rest, or heaven forbid, pay for a product if at any point you decide you like what you're seeing.

Again, I'm not going to blanket defend wavedash studios and I still think the global staggered release is the most moronic and hype killing decision I've ever seen in a gaming company, almost on the level of EA's "pride and accomplishment" statement, but icons has some damn solid framework in place and absolutely deserves the price of the complete package for those that wish to support it.

tl;dr, grind or buy (one time reasonable price too rather than $10 a character, ad infinitum) is a perfectly reasonable business model.