I agree with the 1st paragraph.
2nd paragraph, not so much. It's not that I'd argue against it; just that I think it's impossible to compare different eras. How do you compare coaches like General Neyland, Knute Rockne, Bear Bryant, Bud Wilkinson, or Tom Osborne to Nick Saban? It's impossible. They coached in a completely different eras without nationalized recruiting, national TV broadcasts, recruiting services, social media, readily available game footage of every high school prospect, etc, etc, etc.
If you put Saban back into 1930 or 1950 or 1975, he may not be nearly as good. If you put Knute Rockne into 2021, he might not be as good. It's just impossible to compare because the attributes that made "the greatest coach" then are completely different than today.
Even someone like Bill Snyder is impossible to compare to Saban. Bill Snyder probably doesn't win 6 national championships in 12 years at Alabama, but I'm also willing to bet you that Nick Saban couldn't have done anything close to 108-29-1 at Kansas State from 1993 to 2003. Does that make Snyder the better coach or Saban?
There are too many apples to oranges comparisons in college football coaching. What we can say is that Saban is the greatest recruiter of all-time and he's the greatest coach of this era. But I'm not convinced that you put him back in some previous time and a different place in college football history, that he's anywhere nearly as dominant. Hell, a lot of the flaws of his coaching were exposed in the NFL, so we know he's far from invincible. Loading up on an ungodly amount of 5-star athletes makes up for a lot of other flaws; that wouldn't have been possible in the college football world of 1950 or 1975.