That's hardly true. The neurominadase inhibitors are not the only drugs with some efficacy and are only one class of antivirals. Amantadine and rimantadine, of course, have been effective against certain strains. The Russian Arbidol has as well, but it is unfortunately not recognized as a prescription drug in the U.S.
I meant to add that other antivirals have been in development but were dropped for financial reasons. I think I read that each major pharmaceutical company had at least one.