“Barkley and Henry can make good teams like Philadelphia and Baltimore even better, although are mediocre teams going to become a contenders because of players such as Barkley or Henry?”

While it is true that the effect of an elite RB really shows itself on a team that is already loaded on O (see CM and the 9ers), you can make that same argument about any other position. Has JJ made the Vikings a contender, for example? Any single player can only move the needle so much in terms of elevating the team (case in point – prime Aaron Rodgers only having 1 SB to his name). OTOH, any team that is already very good in a particular unit (O or D) will only become significantly better if you add an elite player to that side of the ball.

It is a bit ironic that despite Barkley’s heroics, the Eagles actually had a better offense in 2022 with Sanders at RB.

TL;DR – there is no single magic pill in making a contender.

I never wanted to face either Peyton or Rodgers in their prime. They would come to the line, read the defense and call the right play, pass or run.
And neither had a RB like Barkley.
Adding Saquon to a team with a very good OL, elite receivers AJ, Devonta, plus Goddert, (and recently Calcaterra) led by a competent Hurts should the offense unstoppable. Or at least average 30 points a game.
The 22 team had a much, much improved Hurts playing like an MVP, Barkley is playing like one.