On the one hand, there absolutely are some places where Linux has so dramatically improved it's insane. Apps like Lutris have really blown me away, it's incredible how some popular multiplayer titles like World of Warcraft which used to take me hours to get running back in high school can now practically run out of the box.
On the other hand, one of the major gpu manufacturer's still has terrible driver support. Systems like Proton are imperfect, and seem to be depressing interest in making native Linux clients. Even though some things work out of the box, you can just as easily spend months failing to get a modern title running. To argue it's the best gaming system is just laughable. In some respects, it hasn't progressed at all in the last decade. When it gets to a point where users can run literally any game out of the box without any additional hassle, then it will be the best gaming system. Until then, this is a gross exaggeration at best.