Interesting concept. Here are the players form the Suns opening roster last year that are still in the league (as a definition of real NBA talent).
Booker
Ayton
Jackson
Warren
Bridges
Holmes
Daniels
Ariza
Melton
Okobo
Crawford
It will be interesting to see which of these players actually make NBA rosters this year.
So --only 4 were not real NBA talent might be an exaggeration, unless I misunderstand what you mean by that phrase. If you mean "worthy of regular minutes" I would have to rethink it of course. Not trying to nitpick here, its just July.
I am not sure what an actual definition would be or what the best phrase to use would be, but the difference between Saric and Anderson (or Bender) is pretty significant. Difference between Rubio and Canaan, Okobo, or Melton is a pretty significant one. I suppose a "legitimate NBA rotation players" would be a bit more accurate than "actual NBA players". Either way, Suns had nothing after Booker, Ayton, Bridges, and Warren until Johnson and Oubre showed up. I suppose Holmes and Melton were good bench players that may qualify as "rotation" players too, but after Booker, Ayton, Bridges, and eventually Oubre and Johnson, there wasn't much on the roster last year.
In my opinion, they went on that one run because they finally had five NBA-level players, and a couple of defensive/ energy players off the bench. Johnson, Booker, Oubre, Ayton, Bridges, Melton, and Holmes were the contributors last year. Jackson played better towards the end of the season too.
Now they have Rubio and Johnson at 1, Booker, Bridges, and Oubre at 2 and 3, Saric, Kaminsky, and Diallo at 4, and Ayton and Baynes at 5. That's nine to ten actual NBA players on the roster, depending on how you look at Diallo and Kaminsky. Then they will also have two older rookies who might be able to contribute. That is a significantly improved team.