Also remember that in past seasons stacking armor and HP were viable strategies,
To about the same degree as it is now. However, even if I agreed with you, I'm not sure this is really relevant. Regardless of which stats have been ideal for tanks to build, tanks have been willing to purshase utility items.
tanks had the innate tankiness to afford to buy team utility items.
Innate tankiness isn't really the deciding factor. The strength of team utility items that have tank stats is generally the deciding factor. When Righteous Glory was strong, all the tanks bought it even though it wasn't the best tank item. When Runic Bulwark was strong, people bought it even though it wasn't the greatest tank item. Same thing applies here. Team utility is something tanks want. They usually can't get items that have it alongside good tank stats, but when they can, they snap it up (unless the supports are already taking them first because support itemization has no choices, like what happened with Locket last season). That's why Locket is starting to see major play on a lot of tanks. Supports have better item options, and Locket combines efficient tank stats with a great active. Tanks want that.
Now carries can shred tanks given the right items,
They always could. Season 2 isn't called the golden age of AD carries for no reason, and that's when tanks were happiest buying team items.