How to manage storage in iCloud

I have the basic 200gb plan.

Without asking a million little detailed questions of how to manage iCloud storage, my main issue is this:

I want to back up my iPhone, the only device I back up. It says I have used 179 gb of iCloud storage. I try to back up my iPhone, and obviously it says not enough storage. Duh. So I'm stopped cold. I have enough space for about one back up at a time. Why doesn't it delete an older back up to replace with a new one? Wouldn't that be automatic? Why would it force me to store and maintain an older back up, when obviously a new back up would replace this? (Or at least ask what I want to do?) Instead of just telling me "You don't have enough space." Why doesn't iCloud ask me if I want to remove and older back up to make space?

And if it's not going to guide me through that, how do I delete an older backup to make space for a new one? I can't believe I have to do this manually.

Thanks for any guidance.