Absolutely Jim! So many manufacturers are using MIM and castings for just about every small part in a 1911. Now we are seeing broken extractors, ejectors, slide stops, thumb safeties, grip safeties, and none of this is necessary. Unfortunately, enough of us want cheap 1911's and the only way to make a 1911 on the cheap is to use the least expensive parts. That means castings and MIM.
A well made cast steel receiver seems to work well, almost as well as forged. You cannot get nearly as nice of a polish and blueing out of a casting and swaging and peening the slide rails on a casting can risk cracking the receiver. A cast slide? There are tons of them out there, some work, some crack in short order.
As for the extractor, I'll take bar stock over cast or MIM, but I agree, spring steel is what John Moses Browning used in his design and that is what works best for internal extractors. Kimber, S&W, Dan Wesson all went to external extractors. Are they better? No, unless you plan to use MIM or cast extractors to cut costs.