Without the Covenant War, what happens down the line with the Innies?
The carver report says that the situation will devolve into full blown civil war unless the UNSC develops a way to decapitate the Innie leadership. The Spartans were the answer. Most people seem to agree they would have worked and the Insurrection would have fizzled out of fear of the Spartans. But the Spartans don’t address the root cause of the insurrection which was the outer colonies being subservient to Earth and the Inner colonies.
Sure, constantly crushing the rebellion will cool things down but the fundamental causes still remain. As far as I’m aware, The UEG and UNSC had no intentions of ever addressing the problems the Innies had and just filed them away as trivial reasons the Innies blew up into rebellion issues, while choosing to just send fleets and Spartans to any rebelling world.
In real life, constant military crushing may temporarily end rebellions but inevitably military force stops working and the government either has to properly address the grievances or decide to cut its losses and let the rebels have their freedom.
The only outcome I see happening is that years, decades, maybe centuries down the line, the UNSC and UEG become rightfully known as authoritarians who will destroy entire worlds and their populaces for their grievances, leading to a full blown outright Civil War that will devastate the UEG and lead to its collapse