If your routing is slow have you tried to reset it by pushing the button either in the back of your router or sometimes it is in the front. It will reset your router. You can test it then or it could be that your internet has slowed down through your provider. You can call them up and asked them. Or yes you can get another newer router.
You can also go to the site that has your router on it and make sure your firmware version is updated.
Also remember that unless you have high speed internet and it is peak usage time that will slow down your internet also.Once again if you have reset your router, changed out Ethernet cord and contacted your Internet company then yes it is time to replace your router.