this is the dumbest question I’ve ever heard. Of course not. it is not the using free models that is the bad part, its the intent behind them. You cant make a game using only free models not only will it fail if you try to but it shows that you didnt have drive or ambition. so to answer your question
Free models are only bad if you don’t try. to make something new. if you are building a city and you use some free model trees, that’s ok, if you import the city, and do nothing else to it that is bad.