This is a common viewpoint of someone who hasn't actually seen their arguments.
It started off as a more generic "we've never successfully made a vaccine against coronaviruses before, this needs more testing to be sure we don't have the same problems as those old attempts".
Then they started noticing patterns no one else was willing to address, like in 2021 countries kept having massive covid waves after reaching high vaccination rates. It was obvious they weren't doing what they were sold on, yet this never got addressed. Instead they were just called "anti-vaxxers" and ignored.
Around the same time they noticed the spike in myocarditis in young men, and only now, over a year later, are people talking about it.
They refer to research and public numbers, they use archive sites to keep things available from official websites that get deleted, and yet are constantly dismissed as "anti-vax" when they have evidence no one wants to look at and actually try to debunk. They just get ignored through ad-hominims instead.