This is still subjective. Some users would prefer to see consistency across all sites they visit rather that consistency on the same site across all browsers.
When every site uses it's own reset there's no consistency while in the same browser, which is way more common for most users that don't have a separate browser for every site they visit.
This is one of the main use cases for reader mode for me—I already have an ad blocker to remove noise, reader mode means I don't have to deal with whatever each random site's designer thought would be the most readable thing, I can standardize all my reading in a format that works for me.
When every site uses it's own reset there's no consistency while in the same browser, which is way more common for most users that don't have a separate browser for every site they visit.