You will also hear "football is just a game", and people who are rabbid football fans will go off. Say "it's just a cell phone" and the tech-heads will scratch their heads. Say "it's just a dog" and pet owners will assure you that it is not. Oh, and let's not forget, "it's just a Mustang".
You see, it is only "just a car", "just a game", "just a cell phone", "just a dog" or "just a Mustang" to anyone who does not share your enthusiasm for that particular thing. There is nothing wrong with that and you should not be offended when someone makes a statement like that. What matters is that
you feel that it is not "just a car". You can also take comfort in knowing there are likely thousands of other people who share your opinion who you will never meet. Possibly 1 or 2 on this board.