Do you not acknowledge that teams like the Lakers, Dodgers, and Yankees make significantly more money in merchandise sales, tickets, advertising and marketing rights, and local tv contracts than small market teams like OKC? They will always have more money. They can spend more, misspend some, and still be more profitable than many teams. In a capless world, OKC could not afford to resign all their players who are getting competing offers from the other 29 uncapped teams, especially those with the deepest pockets like the Lakers and Knicks.
The cap keeps the biggest markets somewhat in check and makes it possible to have a OKC-Pacers finals. If you are advocating for the players deserving a bigger share, they should increase the cap (which they do every year). An uncapped NBA would have all the tier 1 allstars on the Lakers, Knicks, and Heat, tier 2 allstars on the Bulls, Nets, Clippers, maybe Celtics, and 20+ teams hoping their draftees and low tier free agents can compete until said draftees bolt for their own mega contract in LA or NY.