It depends on if the GM rules magic resistance applies to the grapple save or uses a legendary resist after maybe failing. With a level 5 slot it's only 2d6+casting mod with an extra 2d6 per slot level above 5. I've seen players think it was going to be a serious win button only to have it go over as kinda meh compared to something like web. At the levels that 5th level & higher slots are being thrown around 2d6+5 (avg12) is one point shy of what the fighter's getting on one swing with gwm & a +1 greatsword with 1-3 more swings. It might make a wizard feel good, but alongside things like GWM/SS or agonizing repelling blast it's not especially noteworthy,