Except it isn’t. He had goblins and mantid in his ranks during the events of patch 5.4. He kicked the other races out because they rebelled against him. This is something you are ignoring intentionally because it does not fit with your narrative. Hence why you keep ignoring the fact that some of his advisers, like Cairne and Vol’jin made death threats nearly in his time as Warchief. With Cairne even challenging him to a duel because he did not like the way Garrosh was taking the horde. Such as the new assaults into Ashenvale because Garrosh wanted the horde to live with an easier access to resources, not a desert like Durator. This is extended into MoP where Garrosh wanted to “paint the continent red”. Aka, expand and secure resources.
But let us just ignore those valid and canonical points because, “Brown orc bad”.
Only one instance is contradictory, but at the same time it isn’t. During the divine bell finale, Garrosh re-enforces the need to inflict violence only if it is needed and “honorable”, a callback to the stonetalon story line.
Ishi says: Why should be be slaves to honor, when we could slaughter the children of our enemies while they sleep? My blade thirsts for Alliance blood!
Garrosh Hellscream says: Control your hatred, Ishi. There is killing, and then there is murder. Direct your rage to our enemies.
Garroshs’ motives was always about giving the orcs a better place to live.
Ishi says: Do you speak the truth, Garrosh? Can the Horde truly survive another war?
Garrosh Hellsceram says: Doubt is for the weak! Do not question your strength, Ishi. We will survive because we must! The Horde will prevail!
Even his death cinematic drives this home when he says “What I did, I did for the horde”.
That sounds like a you problem. You have to remember, two of his advisers showed aggression towards him. One of whom challenged him to a duel and the other made death threats. How exactly can he trust members of those races who’s leaders challenged his authority as warchief?
Also Garroshs’ motivations were not solely based on “orcs are superior, other races are lesser”. He had goblins in his ‘true horde’ and even allowed Mantid to join his ranks. He rewarded those who showed loyalty.
Except it does fit naturally with his character arc. You have to remember that Garrosh went down an emotional rabbit hole so bad that even those who cared about him viewed him as a lost cause. Everything they tried to do did nothing to convince him otherwise. He was consumed by fear, despair and doubt. Something to note, those same 3 emotions I listed are the same 3 sha realms Y’shaarj takes us to (including Garrosh) during his encounter. Garrosh even remarks,
“See the visions of fear, despair and doubt as I have!”.
How would you react if people your predecessor left to advise you made death threats and challenged you to a duel. How would you react if someone (like Sylvanas) disobeyed a direct order not to use a WMD like the blight to quickly win a war? Garrosh ended up surrounding himself with people like Malkorok because they never questioned his orders. In the end Garrosh was alone. Not every character is meant to have a positive character arc. Not every character who goes down a negative character arc is meant to have a “redeeming moment” at the end. Garroshs’ vision of “orc is best” came from how the other members of the horde conspired against him from the moment he was made Warchief. He never wanted the position, but he was willing to try and do his best. Unfortunately, those around him did not like the direction he was taking it. All he did was to secure resources for the horde. And in the wake of the Cataclysm, securing resources was going to be tougher.
This is not “romanticized” like you claim. This is all canonical lore.
I have no idea why I even replied to be honest. It would seem I will never change your mind, but it was worth a shot.