I would not say grades are by far the most important metric for law school admissions. They are important, but LSAT is right up there as well. And of course, the undergraduate institution matters as well. You won’t get into HLS with a 4.0 from a no-name school, unless you’ve got a 175 (out of 180) on the LSAT.
But the power of the LSAT may wane, as they are removing the logic games, which was a big differentiator.