Wasn’t “allowed”?
Explain, please.
Michael B Jordan, the guy who plays Creed is also directing it. He wants it to be a solely Creed franchise now, feeling they gave Rocky a good enough send off in Creed II. The producers and film company agreed with this, and boxed Stallone out of the film. He'll get a "based on" and producer credit, but won't be in anymore films if Jordan and the other producers have their way.
Stallone himself wants to do a Rocky Prequel series for Netflix or similar. 10 episodes chronicling young Rocky's life.
Stallones's brother Frank a few months ago -

.