I get what you're saying but you really cant fault Feige for wanting to have his moment where he finally gets to see his vision through how he always intended it to be now that he has access to all the toys. It would have been a missed opportunity to not put RDJ, Jackman, Evans, Toby and others in the same room at the same time. And he has the right storyline for it. And the truth is that there are more people than you that want to see these versions of the characters interact before you recast them.
Feige definitely should have recasted T'Challa though but that wasnt the only thing that held back his plan cause SONY was hijacking Holland at the time as well. But he definitely shoulda stayed the course with the Spiderman, T'Challa, Capt. Marvel vision even with the multiverse storyline cause at least the audience would have had a clear cut idea of who are the important players.