I have my main desktop on a hard line, but my wife and I each have a cell phone and laptop that we use all over the house. And, despite having a rather expensive signal booster, the wifi is absolute garbage on the far side of the house. There have even been times where I've been in my office, 16 feet away from the router and the signal is from 2005.
Modem/Router is in the open and not overheating. But, it is 4 years old and I do now wonder if it's just not capable of handling the speeds anymore? Did it wear out? I dunno, its a fucking ton of money per month for super fast internet that is not super fast.