You’re right...hand‑fitting made a huge difference. MIM and modern production methods have their place but they don’t replace the feel of parts that were individually matched and tunedOlder quality guns were made better as gunsmiths actually fit and assembled them. Today with the advent of MIM (metal injection molding)process for manufacturing no so good with no gunsmiths assembling them.
Some of those early doubles were built with such care that even a century later they feel unbelievably smooth. It is pretty hard to replicate that level of fit today.I'd say they are made better for sure. I own a AH Fox Sterlingworth 12ga double from 1917 and that gun operates smoother then just about any brand new gun I've ever held. The quality and fit of the parts is pretty impressive, it is just put together so well.