I don't agree with you guys about much, but we're on the same page with the killing thing.
It's very frustrating, not because I'm bloodthirsty (although I am) and want random ultraviolence in TMNT (I do), but because it takes some of the natural-ness out of the concept and can lead to narrative awkwardness.
I'm cool with non-killing Turtles but I feel like it needs to be baked into the overall concept better. Ninjas don't HAVE to kill, they still have the stealth technique angle and espionage and spying, that stuff is awesome and fun even without the assassination part. I actually tried to accommodate this in-universe by having Raph and Leo trade in their weapons for tonfa and bokken, respectively, but it fell through (you can even see Leo with a bokken on the #103 cover). Like might as well go all-in with it and have that be part of the characters' mission statement like how Batman does it, right?
But eh what can you do, that's the nature of licensed comics, you gotta play within certain boundaries. BUT that doesn't automatically mean the material is bad or compromised, it can still be its own thing and regardless of the restrictions I'm still having a blast doing TMNT. I get to do like 98% of what I want and that ain't bad, haha.
As for the "edge" thing, I feel like that doesn't really mean anything. If we're talking about edginess as in grittiness or whatever, yeah I guess IDW has lost that, but in terms of the regular definition of edginess being like "being at the forefront/experimental/etc." then I think IDW TMNT sort of is, I'm definitely trying a lot of stuff that's new to TMNT and stuff that's connecting with a lot of new younger female readers. That's pretty fresh, for better or worse.
I guess for the "edge" you guys are talking about, though, I don't think IDW TMNT ever had it. That's not a judgment call, it just is what it is, TMNT hasn't had that kind of Mirage-style grit since volume 2. Even by volume 4 I feel like it had lost it, or rather moved on to something else (which was fine because I love volume 4!!!). Then TMNT going to Viacom was definitely the nail in the edgy coffin, future TMNT incarnations will probably never have that again. But I think that's okay, it can be something else that has its own value on its own terms.