Even if we could magically rid the world of everything over 10 (or 20, whatever number you want to use) round capacity, a criminal could plan accordingly and carry more magazines. Those of us who will be using them for self defense or defense of others don't get to plan when we are in such a situation, so this either puts us in a more dangerous position or requires we carry bunches of magazines at all times
That is exactly right. The defender needs the extra rounds. the criminal has the advantages of surprise and usually some planning. While criminals as a population class are often stupid, there is a Darwinian effect and the ones not in jail and on the streets have been selected for intelligence or better than average planning.
A high trained law enforcement person who can perfectly Mozambique a paper target at good distance 99 times out of 100 at the range is going to fire his 15 or 20 until empty in an exercise approaching reality.
Conversely a school spree shooter with two 45 cal 10 round mag pistols and a couple dozen loaded mags can kill huddled children en masse with impunity.
The impulse on mag limits comes from a) ignorance of how weapons are used differently by attackers and defenders; or b) gun grabbers view that murderers and gun owners are in the same class of persons; or c) both