And just what the hell is wrong with fanservice? Seriously, I'm asking this as somebody who sank hundreds of hours into FE Awakening's Lunatic + Mode. Not every games needs to be a ball-breaking-dominate-your-life challenge.
Oh, there's absolutely nothing wrong with fanservice. Only when said fanservice is just that and basically
nothing else to swallow with it. It may be great to see all these famous characters in one game, but if there's little-to-no strategy in a STRATEGY game, then... it's not justifying the genre at hand, now is it?
Again, like I said before, ALL SHOW AND NO FLUFF. There's no point in playing a game that can't deliver a challenging experience; or rather, no point in playing a
strategy game that can't deliver a challenging experience. No, it doesn't have to be a "ball-breaking-dominate-your-life challenge" like Awakening's Lunatic modes, but it should still offer a substantial enough challenge to make you feel like you're actually accomplishing a risky and exhilarating task.
it's REIJI AND XIAOMU MEET X AND ZERO, that's reason enough.
Plus Iris. 
"That's reason enough"? Was it really that simple to make you cough up dough for this?
What little strategy there is really has little to do with the map and more to do with how you time your attacks in order to do the most damage (and/or milk the most XP to enable skills/attacks later). It's simple, yes, but it's more engaging than you might think.
Nobody who's ever played Yoshi Story judges a game solely by it's challenge, and I suppose PxZ may be best described as the strategy equivalent to that. While it's extraordinarily difficult to "game over", there is definitely an advantage to knowing how to manage your attacks, items, and skills. Beat down the optional high-level characters and you get better items to use later. But if you want to suck and get by on the minimum, well, you can probably still clear the levels without too much trouble.
Never died yet, and it's rare that I have to "revive" a fallen teammate. But I will say this: KOS-MOS's intro level was pretty nerve-wracking.
From what I played in both eShop demos, it is indeed engaging to manage attacks and such. Well, even if you could only manage as much as a demo allows.
But I can tell it gets old after a while. As I've also heard from many other people that have actually beat the game.
Once you get the juggling times down and manage the XP gauge with ease, there's even less challenge than what you start with.
First and foremost, this is a STRATEGY game. If it's extraordinarily difficult to get a game over, that says it all. It fails what it sets out to do. Managing your [parasitic bomb] will make the game easier than the already easy experience.
You said it yourself: if you want to suck and get by on the minimum, you can probably still clear the levels without too much trouble.
This game takes a dump on the strategy genre.