There's really no solid data to back this up. The only randomized controlled trials that were ever conducted ended when the EUAs were granted and the placebo groups were immediately vaccinated, long before the Delta variant even existed, let alone Omicron. Everything else is observational studies subject to selection bias and other confounding variables. And even there, the proportion of vaccinated vs unvaccinated deaths from Omicron (where good data is available) does not suggest high levels of protection from the vaccine.
It would be truly remarkable if vastly decreasing the prevalence of the pathogen early on somehow kept you from the hospital but led a far less extensive infection doing just as much damage. Posting solid data here when literally everyone on the forum has sought out such data at one time or another is a waste of everyone's time. If you have succeeded in ignoring it at this point no data is liable to change your mind.
In any case : vaccine-induced myocarditis is almost always benign and resolves without treatment, and while there's been a lot of focus on it in the press and in antivaxxer circles, it's really a footnote in the list of Covid-related health issues.
It's many orders of magnitude less frequent than Long Covid, for example.