To be honest, the oem aluminum cast frames weren’t very good either. They had poor quality control and had a lot of impurities and bubbles in the cast molds. When I’d send them for Np3 plating, many would look like Swiss cheese with hundreds of pits.
The A&S frames have been a huge step up in terms of functional quality and appearance.
I got my first M4 for 1300 bucks in 2004. They go for a lot more now. I’d say the newer production units are better than the old ones. I had so many issues with my first one that it went back to Benelli twice. I broke pistons, I beat the bolt carrier to the point that it was mushroomed around where the pistons hit. It came with that lame neutered receiver extension even though it had a fixed stock. About the only thing left from the original is the receiver.