Why is the US Economy Sort of Sluggish?

The article, written by Kevin Drum on the date of October 10, 2016 on the website motherjones.com, says that our recent sluggish growth is mostly a result of technological slowdown and demographic changes. The retired population has increased while the working population has decreased. Due to that population decreasing, the GDP growth will also slow down. If less people will be working, does that mean that taxes will be raised so the government can pay for stuff they've always been paying for? The only thing that's hard to say in this situation is whether or not prices will be raised on products because people that are retired still have money for products, but how long will that last with more and more people retiring before their money runs out? Questions like this are hard to answer, but one thing is clear. With a low number of people working, the economy will not go up as fast as some people would like it to.