If you’re copying something then it’s copyright infringement unless the works are in the public domain. If the copyright holder allows it then good, but I am yet to see an IP holder allow organised copyright infringement. The moment someone gets a team or a website together then the cease and desist letters start coming in.
So by all means do fan art, fan-fiction, a solo fan-made game, but don’t expect to put it on Steam or make any money from it.