Mobile is the biggest change in technology of the last 20 years without a doubt. Without it we wouldn’t have always-on connectivity or computing as a utility.
It is the advances in the mobile technology of the last two decades that have seen the greatest changes for the CMS. At first you needed to be able to offer an alternative mobile version of your site. Possibly on a m.example.com domain and certainly using smaller media assets if any at all.
Then as the speed of both mobile data and mobile processors increased there was no need for a CMS to manage two almost separate websites and instead we relied on responsive design principles to serve websites with appropriate media and designs.
Other trends have come and gone over the years but the fundamentals of CMS haven't changed - the ability to quickly, easily and consistently add content to a website.