As COVID has shown, you can't convince the deniers, you have to make politics despite there being people who refuse to share the same reality with you.
Everyone engages in motivated reasoning. Deniers underestimate risk, and their opponents often overestimate the risks.
Getting people on the same page means understanding their motives and framing the facts appropriately. Unfortunately, people just want to take sledgehammers to "the other side", as if that's ever really fixed anything.
Maybe proper productive conversation would be easier if you didn't label the entire population with differing opinion as "deniers ... refusing to share the same reality".
In other words, why would anyone get to "make politics" despite of anyone.
What else can we do? They have a fundamental right to deny all your science by putting fingers in their ears and screaming lalala. And they exercise it. And they have as much voting power as you do. And it's not some abstract bogeymen we're talking about here, these are our uncles, cousins, parents, ...
Proper productive conversation has been tried. People are labeled as deniers not just because "different opinions" but because they don't even share the same sets of facts from which to start. You can't have a productive conversation on COVID mitigation measures with someone that thinks that COVID is "just the flu", for example.
You're right that people don't share the same sets of facts - for example, at least in the US Covid "non-denialists" substantially and consistently overestimate the risk, especially the risk to young people: https://www.brookings.edu/research/how-misinformation-is-dis...
It's far easier to educate someone on correct hospitalization rates and death risks than it is to convince someone that covid is real when they think it's a conspiracy and that vaccines contain poison or something. I don't know why would you want to equate those two things, honestly.
Getting people on the same page means understanding their motives and framing the facts appropriately. Unfortunately, people just want to take sledgehammers to "the other side", as if that's ever really fixed anything.