It's what Chairchucker wrote; brand factor alone means that people who have never played an RPG before still know the general gist of what 'Dnd' is. Like, even if you told potential players you're going for something "Tolkien-esque", it'd be less useful than using D&D as common ground.
With that said, OP obviously has an axe to grind, see thread title and general wording of their post. Using 5e as a gateway game to get people to try other systems is perfectly fine, but you have to argue persuasively that the new system is "better" than 5e. If you've got a player who's experienced with 5e, but disgruntled with specific parts of the system (Simulationist aspirations, dated progression system, etc), then you could totally put together a persuasive argument that they should let you run something else for them.
Everyone's who's played 5e has something they hate about 5e.