It is often considered a "narrow" tax base - just not enough for a "single" tax, all things considered. (That's largely because the burden of existing taxes is already being borne by land, at least to a significant extent. They just have additional disincentive effects, quite separate from that sort of final tax incidence.) But even then, it's clearly enough to fund local government expenses, so there's really no excuse for why we aren't using it.