Fair question. My guess is that the vaccination requirement, without requiring a booster shot, is likely having a minor impact on reducing spread, since we've seen significant waning in preventing infections from 2 doses (and from previous infection), although we haven't seen much diminution of protection against severe COVID/death, given the complexity of the immune response; boosters however, still show significant reduction of infection and likely many fans have been boosted, so the overall effect could be a modest reduction from requiring vaccination. And the mask requirements are likely having a minor impact on reducing spread, since masks work, but imperfectly and compliance is good, but not great.
Combined, the two maybe are having a moderate impact on reducing new cases resulting from attendance at the RAC. I couldn't put a number on it, but maybe a 30-60% reduction? For me, that reduction is more than worth the tiny inconvenience of taking a few minutes in line and wearing a mask, especially since many fans then go home or to work and are in close contact with others who might not be vaccinated and could then infect them, which would be bad, as they're at such high risk (if not previously infected).
But it's also worth adding that this is all changing very fast in that we likely just went through an omicron peak that saw close to 6MM New Jerseyans (66%) get infected with omicron (assuming 20K infected per day for 30 days = 600K times a ratio of as many as 10 people actually infected per infection recorded by testing, given the very high asymptomatic infection rate). Meaning we likely prevented some cases, but those numbers were likely tiny compared to the transmissions going on elsewhere, especially where such controls were not in place. Doesn't mean we shouldn't try, though, IMO.
But also, given where we are now and will be in 3 more weeks, so many will have been infected with omicron that continuing with mitigations eventually makes no sense, as the vast majority of people will have immunity from omicron based on either infection or vaccination (especially those boosted). Which is why I see controls and mitigations winding down now/soon and I think that makes sense.