They’re probably not going on “player feedback” in the sense of asking players. They’re probably using detailed analytics via Steam on how people actually play the game. My suspicion, given that Chimera exists, is that their analytics show that a lot of people actively reload if anyone they remotely like dies, and some people likely do if anyone dies. I suspect the analytics also show that a lot of people aren’t that interested in the base-building stuff, given how they’re trying to pare that back too (I’m certainly with them there - base-building is boring, dumb, and frustrating in both the the nuXCOMs).
Calling a 1/4-1/2 price experimental sidequel to a series which will definitely see an XCOM3 a “complete betrayal” seems like, I dunno, a bit dramatic? Especially with the comparisons you’re making. This is hardly Fallout 2 to Fallout 3, even. I mean, I guess I got over your issues a few years back, I’m not totally unsympathetic, but they murdered my '80s and '90s games long ago, and they even murdered my favourite game series ever, Mass Effect (they’re probably working on a new one, but it seems like it will contain Andromeda elements, so may well suck), quite recently and shockingly. But I don’t think that’s really a reason to feel “excluded”, just because Firaxis put out a low-price experimental XCOM game whilst developing XCOM3.
Realistically, if the design of XCOM3 changes because of Chimera, I think it will be because Chimera was very well-received by the majority of people who bought it. If it isn’t very well-received, then I don’t expect it will have much impact on the design of XCOM3. Firaxis aren’t idiots, and they’re very keen on making money. If “most players” as you say, are more like you and like people dying and stuff, then I’m sure that’ll stay.
What I actually expect re: XCOM3, death-wise, note is something in-between. I suspect either death won’t be a thing on the “normal” difficulty, perhaps a toggle entirely, or I think more likely you’ll have some system for mitigating deaths. I.e. either they’ll have some “named” story characters who don’t die, or they’ll let you tag certain character, or use a resource, to prevent deaths.