There are currently six known quarks: up, down, strange, charm, bottom, top. Only the first three were known before the second three were predicted by theory in the early 70s; they were all eventually confirmed by experiment, but the top quark wasn't found until 1995.

That's one example of how powerful the predictions of theory can be; there are many more. Obviously, there are a lot of incorrect theories, too. It may seem like physicists just invent new particles to solve any problems, but no matter what we hypothesize, it all comes down to what the experiments show. So far, we have found many predicted "new" particles in consistent ways (although the list of particles that have been proposed and never found is very large indeed).

The Higgs mechanism has been around since 1964, along with the prediction of at least one new particle to go along with it. It's only now that we have the technology to probe the high energy range at which such a particle could be seen.

Don't get caught up in sensationalized news reporting, which makes everything seem like a brand new invention. (To be fair, this was actually one of the better mass-consumption science articles I've read recently.) Most of the theories for which we'll soon be searching for evidence have been around in some form for decades now, being refined and probed.