Let’s clear this up first. Your core does not equal “abs.” You can have a strong core with no ab definition. Opera singers can manipulate their core to sustain notes, but Pavarotti has no visible abs. Core exercises, alone, are not going to get you shredded.
Over the last few years, the plank has become the “go-to” core exercise. Countless articles have been written about them and hundreds of people perform them at the gym every day.