1) This is an irrelevant statistic.
2) Even if this were true it's not that big of a deal.
This is irrelevant because most people don't browse the average web page. They browse the top few sites on the internet and that's it. A more relevant statistic would be what have the sizes of the top 50 sites been over the last 15 years. I imagine they still may have grown on average, but download speeds have also grown over that time. Especially on mobile.
Even if we accept the premise that web sites as a whole, including the most popular ones are all growing and are now an average of 2.2MB each. Who cares? 2.2MB is nothing in 2016. Even on an LTE connection that's probably between 4 and 1.5 seconds to download the full page. And a lot of that size is probably in ads, which nobody minds if they load last or not at all.
Lastly, this is a self fixing problem. If a site is too bloated, users will stop going to it.
But I would propose that a lot of this increase in size is due to users (especially mobile) having higher and higher resolution displays, which necessitates higher resolution content, which of course is bigger.