You are offering a strawman. Being capable of adapting to future situations requires understanding "our reality" and projecting where that could take us in the future. Ignoring what is currently understood of "our reality" to postulate alternative universes doesn't do that.
It's sorta like the difference between good hard science fiction and science fantasy.
A lot depends on whether the metaphysics are the same.
At any rate, your Incredulity at the very idea makes it apparent that you would have a harder time coping with whatever of.the infinite possibilities are true, if any.
Personally, if I find myself standing in front of a god, I won't find myself at a loss for words, or the reasons and convictions to actually say them. Nor would I be particularly unable to adapt to whatever logic is necessary to live as an alien butterfly, assuming I survive as an alien butterfly for long enough.
It is the difference between being caught flat-footed, and being able to adapt. Because if I AM the dream of an alien butterfly, that butterfly has some serious computing power available to it.
You might as well be a bronze age dude asking how the hell we can have less than nothing of something and thus why do we need negative numbers. Your inability to expand metaphysics and logic to other contexts would suck for you. Not so much for me.
Perhaps it comes down to the practical value of actually having, and exercising, the imagination.