Are you prepared to get sued by Stephen Spielberg should a Tolkien esque story emerges by coincidence?
That didn't work when Marvel tried it against City of Heroes, and costumes are far more copyrightable than "a Tolkien-esque story". Keep in mind, something has to be clearly defined for a copyright or trademark, and "it's sort of like this other story" is
really hard to prove to a judge or jury's satisfaction.
The Tolkien estate has sued to keep fictional names of creatures for which Tolkien created names, but renaming balrogs into balors got D&D off the hook, and "orc" (originally Tolkien's Elvish name for "goblin",) is completely public domain at this point. Stories that are
like Tolkien? Yeah, that' not easy to win.
Beyond that, copyrights don't work if there are at least five other examples of sufficiently similar design. HOW many Tolkien-esque stories have been written in pulp fiction, now? Hell, Angband, Moria, and ToME outright
are LotR games, and they didn't get sued.
Beyond even
that, Spielberg would actually have to know that DF exists, and he's too busy pissing all over the works of fans of his own intellectual properties' legacies to care looking out very hard for Tolkien's.