The reason there's a plan...but it's fluid... but prayer might help, but it might not,. ..because of this fluid plan...
is because God just doesn't exist - except in the minds of humans.
Just as time only exists as a concept - yes, the passing of moments exists, but 3 o'clock doesn't "exist". it's a human construct to help us understand the passing of time and all that.
God is just a human construct to try and help us understand the world - be that in the form of Yahweh, Freja, Zeus or any other god.
The problem Christianity has, is that it's rule book is fundamentally flawed, it was written by various authors at various times often decades after said events and without contemporary evidence. It's been translated, edited to exclude entire books, edited to suit a narrative... It's mish mash of nonsense, which some people "believe is true". And consequently get themselves stuck when asked hard questions, so have to resort to "God has a plan... that is fluid... that we can never know or comprehend ..but also free will. but also the plan"
you may as well, grab all the books you have right now on your bookshelf about well being, self-help and mindfulness, cut them up a bit, stick them together and call it the New Bible and start a religion from it.