Although he was a 123-year-old gray dwarf who was weak, helpless and a little bit of a gluttonous child in his parent's eyes, Ironfelt actually had experience that matched his age as a craftmaster. Even if he had not been to the surface before, he would hear about it from traveling gray dwarves as they bragged away every other day in his nightly drinking session in the Magma City Tavern after work.
Ignoring the narrators' boasting and cleaning up the stories, the humans depicted in those dwarves' stories were more or less the same. At a rough glance, their lifestyles did not differ much from the dwarves', but because humans had much shorter lifespans, they did not display the same demand for excellence or the same passion towards their craftmanship, and most of them live out their days dully and muddleheadedly under the rule of churches and nobles.
Moreover, the humans were so great in numbers that their gods could only favor a select few, leaving their species weak.