There’s others that are trying, Blue Origin has their New Shepherd rocket that is able to land, but it’s a suborbital tourism vehicle that’s basically just a toy. They’re working on a partly-reusable orbital launcher that’s like a souped up Falcon 9 but it’s still in development. Several other smaller startups are working on smaller Falcon-9-like launchers with expendable second stages, and China is building a straight up carbon-copy of the Falcon 9 and Starship. But SpaceX is the leader in this field and currently the only one who’s actually successful. Everyone is following in their wake at the moment.