I have a half bath toilet that has never flushed properly. Could improper venting be the cause of the problem and if so what are some fixes?

I have one you might wish to check out. In my capacity as shop trouble shooter I began to run into a slew of complaints on our new construction that were just like yours. I knew they all couldn't be " bad toilets" so I went looking for the cause. I found that when installing the new bowl that the wax ring had been forced out into the discharge pipe and blocking the free flow of water. When the water hit it a backpressure was set up preventing the siphon that makes a good flush and the solids just swirled around while the water went slowly down. I had to set up meeting with our plumbers and show them the problem and how to fix it. When you set the bowl, put the wax seal down on the flat side to the closet flange. Then take your hands and bevel the wax seal outward so that when you set a bowl on it the wax is forced out instead of in blocking the flush. The customer complaints stopped and I had less work to do. Try molding the wax seal so it doesn't choke down on the flush. Good luck, Tom