As others have mentioned, it's Larian's design choice to make everything *look* like dodges, and it's silly.
But you asked about the AC mechanic... The AC *mechanic* is that AC represents the total accumulation of you ability to avoid being hurt, whatever that means. If an attack roll does not meet your AC, that means that, whatever else happened, it failed to cause you harm, or you managed to avoid being hurt. It does not inherently mean you dodged; the mechanic doesn't specify how harm was avoided, just that it was, and the how of it is between you and your DM. The character wearing +3 plate armour with a +3 shields and the Dexterity of a head of cabbage, still has 26 AC because they're a nigh impenetrable fortress of metal. When hits fail to damage them, it's generally going to be because the armour stopped it - though it may also be because the attacker just plain missed, too, or any other outlier reason. Armour does protect you - that's what AC is.
Larian made everything look like dodges all the time, and that's pretty dumb; blame their visual design choices for that.
