Simple grind? I don't know what level you're at, but I'm assuming not very high. It can take several days to train one level 10 unit just once. In the meantime, you're facing units in the level 11-13 range. With the current meta and the strategies I'd like to use, Shock Troopers would be a key unit to have. However, mine are stuck at level 9 due to lack of cards. Meanwhile, my opponents have level 11-12 Shock and Flame Troopers leaving mine completely helpless.
As for being a professional gamer in Rivals, I don't see any way to make any serious money off of this game; at least right now. Either way, this game is billed as competitive and a test of your skill. Having unit levels that can be gotten around by pouring money and time into the game has nothing to do with skill. Not only that, it is an anti-skill gameplay mechanic.
It's a shame they've gone this route because the core game is amazing. That's what makes the leveling prices and bundle "deals" so insulting. I would pay $30-$60 for this game to be complete. Any higher is unreasonable due to how the video game market prices games. You can buy fully featured PC RTS games at $60 or less. Why do I need to pay thousands if I want the complete experience from a mobile RTS with no campaign?
If you look at the big picture of how games are priced and what you get out of them this is complete insanity. Obviously those running this aren't insane, so what could be driving them to set these prices? Again, it's obviously driven by greed.
I don't say this lightly. I've never accused anybody involved with a game of being greedy before; I don't make toxic, baseless posts like the ones you see around here. But this is the only reasonable explanation for how the game is being run. The leveling system isn't fun at all, it doesn't add any positive value for the player. On top of that, the prices for the microtransactions are completely unreasonable. Their "big holiday deals" are the price of a decent PC game, and that's at a supposed "2.0x value" discount! Is leveling one unit to level 8 really worth two AAA PC games on a normal day? Absolutely not!
Yeah, I could afford to spend enough on this game where I'd be on par with the higher leveled players. But that's an insane waste of my money and I will not financially support a game driven by greed. It's fun enough that I'll keep playing without paying. But it's wrong to expect to be treated this way just because "I'm a F2P player". I'd pay for this game if I could, but the devs have chosen not to give me that option.