What do you mean “nada is common among them”?
I own a made-in-1955 M70 in 30-06. I bought new in a store a 308 Win XTR in 1976. I also have a "Sporter Magnum" - push feed in 338 Win Mag - made in 1983, I think. And a made-in-1982 Winchester Westerner in 22-250. I have not owned one of those that were made in Portugal or South Carolina. External extractors on the 1955 is spring steel - later ones are reputed to be very soft metal - can bend into an "L" with your hands. Open type triggers on the 1955 and the push feeds - enclosed in a box triggers on the newer ones. And so on. For sure, the general outline and visual, and the brand, might be similar - I guess that is what sells. But they are very different in their details - in their construction - that stuff likely does NOT sell well, as it appears many buyers do not know or care.
Perhaps I am getting jaded in old age, but the M70's, I think - are like many other products - terrific reputation based on what they made in 50's and 60's - then inflation pressure or whatever created a push to reduce production costs - most all changes than go to Marketing who convince the new buyer that the "cheaper to make" is actually "better" - is an "improvement" over what used to be. Often "modern" management is cashing in on a previous generation's hard work to create a reputation - is now being "mined" for the last nickel - then move on and acquire a next company/brand ...
Today, Weaver, Tasco, Redfield, Bushnell, Simmons and perhaps other scope brands owned by same company - not really "competitors" as in the past. FN owns Winchester arms and Browning arms - not exactly "competeing" with each other, except to benefit their owners in some way. None of those items being made by same people, same tooling, same plants as in the "old days", so past experience means about nothing regarding them. Is hard to accept that an item that has given you reliable and dependable service for 30 plus years, CAN NOT BE REPLACED. Even if the brand of the thing still exists, it is NOT the same as what you bought back then.
Something as mundane as metal files - when I apprenticed, the tradesmen insisted the Nicholson files were the "ONLY" files to work with, where we were. Made in USA - about "perfect" for what we did. So when I retired, I "splurged" and bought a Nicholson set for myself - not even all made in same country - some are stamped "Made in Mexico", some are "Made in Brazil" - wavy sides, uneven teeth - but they do have the Nicholson brand and logo on them.