The WBC is every fourth year, in springs following Summer Games; only the first interval was three years.
American interest may be mediocre, considering how great it actually is, but Americans are not the only baseball fans. Asian and Latin interest has been pretty strong.
It occurs during MLB spring training, which of course is only relevant for some players and fans. Not really an interruption, more like an alternate track (and the games are vastly better than ST games, to be honest). The national teams whose first-round games are in North America usually play exhibitions against MLB teams at ST facilities.
Look, I’m a huge baseball fan, especially international ball; for myself, I’d be delighted to see baseball in the Olympics again. But there’s no realistic way that Olympic baseball is going to be better than the WBC.