Why, then, can we not have background checks for everyone, which would simply implement that view, which is supported by 97% of the country?

We do and have for years and they are totally stupid and a waste of time. What is the point of them? Say Nicolas Cruz failed because the cops actually did their job one of the 45 times they were called on him and arrested him and got him convicted of domestic violence and then he failed his background check, would he have decided not to be a school shooter? Would he have been unable to acquire a gun in south Florida? Would that stop him from renting a Uhaul truck?
what's the point?

Criminals and sick people do not need access to guns.

But of course they don't care about the laws by definition so they will always have that access, just like heroin. Should criminals and sick people have access to heroin? do they?

And no one needs semi-automatic guns on the street.
What about Asian women who have to fight of gangs of armed thugs?

Making those changes does not take away the Second Amendment right.
Actually banning semi auto guns would totally invalidate the 2nd amendment and infringe on everyone's basic civil rights.

"Those are the right things to do."
No, doing stupid things that only harm law abiding people and provide zero benefits are the wrong thing to do.