Why does it take so long for a page to load?

This is a typical day for me. I open Firefox (or Chrome) and then try to open Outlook.com (or another site) and I wait wait wait for the page to load. Sometimes it takes 5 minutes for the Outlook message to open once I click it.
IP RCN; 250 mb; Windows 10; Enough memory and storage on the desktop computer.

This is what I see at the bottom the page: Reading banner.advertising.com; Reading ow2.res.com. office365.com; and there's a lot of "reading" going on and it is a wait and see if the page loads.

Can someone tell me what is the problem with getting a page to load up. I'm 90% on the internet. I sometimes use my desktop software (which is faster). This is maddening.
Why so slow?