My old iMac is another story. It's so old it couldn't even be upgraded to High Sierra. I only use it for downloading stuff, but Safari, Google and Firefox can not be upgraded at all. And I had to stop using Safari all together, because it stopped letting me access specific sites that I had been going to for a very long time...kept claiming it couldn't make a secure connection to those sites. I've been using Firefox instead, and it's still performing fine. Knock on wood!
My oldest son used to be a big Mac user, but got tired of Apple's BS, and uses PC's now with Linux. He's the tech geek in the family, but since he hadn't been keeping up to to date with Apple products, I could even ask him for help when my laptop space was disappearing. I'm 71, and cringe every time I think about having to replace one of my old Apple computers. They're not cheap, but I don't know if I'd be able to deal with a PC and Windows.
Sorry about your space problem - sounds like you were doing Time Machine back ups or something similar - as for my space I would not notice since I have something over 6TB divided into multiple partitions.
Replacing my apps would cost many thousands of dollars - something I’m not willing to exchange for features I either dislike or would never use.
As long as FF keeps grinding on all is good - tried New Moon, but when back to FF - I forget why.
I tried many times to upgrade years ago but always ended up either losing important stuff or my mac not recognizing the upgrade - so I quit beating head against wall.
I’ll upgrade the mac when this one either dies or becomes otherwise unusable and will try to find a OS10.6 used machine in good condition at a reasonable price. The new ones cost far roo much with little added benefit for me and a whole lot of app draw backs.