You don’t have a plot without a beginning, middle, and end. That’s… what makes up a plot.
No, but you can have a game of D&D where the DM plans a setting, with interesting people and things in it but not plot or events planned out and asks the players what they’re going to do. And those games are the ones I find I tend to enjoy most.
I obviously disagree. You when you have a beginning, middle, and end, you have a narrative. But, you don't have a plot.
The plot of a story is the reason behind why that story is being told. The plot of Star Wars is to stop Darth Vader from using the Death Star to take over the galaxy (ok, that's a bit reductionist, but, you get the point). Obi-Wan cutting off some dude's arm in the Cantina isn't really part of the plot at all.
But, the point is, once you've got the DM who plas a setting, fills it with interesting people (how are they interesting? Because, by and large, they are going to drive play) and things you have a story. That's what a story IS.
The notion that story=a complete lockstep railroad where the DM dictates every single event is far too restrictive a definition of story. That's not what a story is. If you have a plot, character and setting, you have a story. And just because you have a story doesn't mean that every single detail must be nailed down beforehand.
You prefer a more open story and that's groovy. But, dragging this back to the original point about character death, removing character death as a possibility does not require the DM to suddenly dictate every single element of the game. It simply means that that particular narrative - the character dying, isn't on the table. Is it somewhat less open than otherwise? Technically I suppose. But, infinite endings -1 isn't really much of a restriction.