Surprised at the amount preferring Mario's pay model.
For Fire Emblem, I haven't spent any money and I have 57 unique characters, I beat the story mode and Paralogues and did a majority of them on Hard and Lunatic as well. Only things I haven't been able to do is 2 of the Grand Battles, due to being stupid hard.
The "pay" part is Orbs, which is primarily for summoning. I have been using the same team since I started though. I'm just summoning for the sake of it. Orbs don't help you win, and you get TONS for free all the time. I also have 22 of those things to restore my Stamina, 45 to restore the battle arena, etc. Can also use MyNintendo to get some stuff.
You don't have to pay for anything and it is painfully easy to get more things by just playing.
Not sure what you guys are doing wrong where it is such an issue.
As for Mario, the problem is justifying the $10. It is a watered down Mario where you barely control characters. The "pay once and have at it" model isn't the issue, but $10 for what it ultimately is? Yeah.
It would be like paying $10 for Miitomo so you had free access to all clothes and Miitomo Drop.
Of course Nintendo prefers that pay model. They get $10 from each player, rather than thousands who play the game and pay nothing.
The best method is to follow Pokemon Picross & Rumble World. Do F2P, but have a cap where you can pay to have it all at once. So basically give you both methods. Pay once & free to play.