Actually, that's exactly how copyright works. Works that are found to be substantially similar to the original can be found to infringe copyright. The issue in question is how similar a copyrighted work needs to be, for it to be covered. However, for video games, as well many other fields, such as books, and even board games, the number of elements that can be copyrighted are surprisingly limited. The Copyright Act of 1976 states that:
“In no case does copyright protection for an original work of authorship extend to any idea, procedure, process, system, method of operation, concept, principle, or discovery, regardless of the form in which it is described, explained, illustrated, or embodied in such work.
This effectively means that most (if not all) game mechanics are not subject to copyright protection. Video games such as PUBG only exacerbate this issue, as a significant portion of the game is based on reality and facts cannot be copyrighted. Using a M4A1 in PUBG for instance, there's nothing copyrightable about it, except for the original artwork (and when going for a realistic drawing, as PUBG does, the copyright protection available to that piece of artwork is generally limited to only actual copies).
If you're interested in learning about how complex copyright can be in games, I highly recommend reading about copyright issues with board games.