Best splitter to use intermitant connection instablity

I have reviewed some of the forum messages and I believe I need to upgrade, change out the splitter I have. I get intermittently unstable connection messages while onZoom, my son is lagged out on Call of Duty for about 15 or 20 seconds and our phone intermittently you can't hear the person on the other end for 10 to 15 seconds and it magically comes back.  All these devices are hardwired and not over the WiFi. Mine splitter is vintage 10 years ago and pretty cheap.  It is a three-way where I'm only using two and the third is capped. I have an XFi gateway. Am I on the right track and if so what splitter should I buy?