Unable to back up my iPhone to my Mac

My Iphone is 'full' (aka half full of my stuff, half full of 'system data', which is total garbage and embarrassing that such a 'great' company can't clean up its own logs and caches).

I've tried to back it up to my Mac (not iCloud), and it's also saying my Mac is full. That's total garbage, I have 7.4 TB free and it's only a 64gb iPhone. My Mac is nowhere near full. This is garbage and feels like planned obsolescence somehow to make me get a new iPhone, but I'm definitely not going down that road.

[Re-Titled by Moderator]

Original Title: I can't back up to my mac.