Not wanting photos shared on both iPhone and Macbook

A few years ago I guess I changed a setting in my MacBook and since then all of my almost 25,000 pictures are also on my iPhone. I would like to remove at least 20,000 of them from my IPhone but keep them on my MacBook.

If I turn off iCloud on my iPhone, all photos except for the last 100 are deleted. But I want more than those 100 pictures on my phone. How do I go about doing that? I'd like to keep pictures on my phone but not all 25,000. I would like my pictures to go onto my MacBook, but not to go back onto my iPhone.

Is there a way to make this happen?

I waited on hold for over 40 mins to get to talk to a creative employee with apple, but no response as of yet. Hoping to reach someone here for more information as well.