The rate of myocardits from the vaccine is actually significantly lower than the death rate for Covid for people in their 30's.
The rate for myocarditis for Moderna is about 1 in 24,000. There have been a little less than 15,000 covid deaths of people in their 30's. I'll drop that to 10,000 just to eliminate the risk of overcounting. For the risk of death to equal the risk of myocarditis, you'd need there to have been 240,000,000 covid infections in the US among people in their 30's. There are about 45 million Americans in their 30s.
So if 10,000 Americans in their 30's died of Covid, for the risk of death of Covid to equal the risk of myocarditis from Moderna, you'd need every American in their 30's to have had about 5 covid infections.
So you're actually far more likely to die of Covid if you're in your 30's than you are to develop myocardits.
Oh, and the vast majority of mycarditis cases caused by the vaccine are mild.