Just last week I visited an old friends site. I learned to him more than 10 years ago, how to use my CMS, and he made his site.
Some years ago, I enablaed this new ad forms. This new ad forms had been only for mobiles.
I noticed a Google message, that this new ad forms are now also for desktop.
I did not think on the consequences.
His site had my usual earlier system with 2 * 600x280 ads and 2 * 600x21 AdLinks

But combined with the new ad forms, the site looked completely messed up as an ads only page.

I removed all ads. The changes at Google Analytics are great:
pages per session from 1.68 to 5.49
pages per session desktop from 1.77 to 4.64
pages per session mobile from 1.38 to 7.00

time per session from 0:31 to 1:18
time per session desktop from 0:38 to 1:10
time per session mobile from 0:20 to 1:34