I doubt if age has anything to do it, more likely a hack handyman or a ignorant homeowner. There's little question that you should have a shut off valve on the toilet supply. This is really rocket science, just get the materials needed, and shut the water off. There should be one where the house supply line enters the house, but again, you never know for sure. You may have to go to the street. The easiest valve to connect the the supply line is a compression valve. The pipe does have to be in good condition, no kinks or dents. The most popular valve now days is a quarter turn type.