Except I even clearly drew a parallel between Blackhand and Doomhammer, which was the same Old Horde that had its ways changed to suit that of the Warchief.
Blackhand and Doomhammer have very clear different versions of the Horde, with different established methods. Blackhand was cruel and forceful, Doomhammer much more cunning and tactful. Both sought conquest and destruction, but with very different reasons and methods behind their use, with Doomhammer open to having allies and fostering diplomacy whereas Blackhand was simply a tool of Gul'dan and sought nothing but carnage and destruction.
They were the same Horde, and they functioned differently under each Warchief.
What makes Garrosh's Horde the same as Thrall's Horde? What makes Sylvanas' Horde the same as Thrall's Horde?The Horde that Thrall built is a completely new one, independent and unrelated from the first.
You're trying to establish that the current Horde can only be the same one that Thrall established and never evolve beyond that, yet where are you drawing this from?
Thrall's established Horde is not his to control after he relenquished power. Does this not make sense to you?
The Horde is the will of the Warchief. That the player fought on the side that deposed two Warchiefs that were deemed evil was a case of the writers fucking with their own lore; a Greedo Shot First retcon of events that shouldn't have happened in the first place. As a point to not fucking with the canon, a Faction civil war story that is meant to split the faction should never have been told if they aren't able to carry through actually splitting the factions. As I said, the Forsaken story works in WC3 because the RTS campaign story is self-contained and they are able to canonically split the Forsaken away as their own independent force. This would never work for BFA because the Sylvanas Loyalists are still gameplay-bound to being Horde players, no matter how you cut it. And really, incoherrent story writing in portraying how much power and influence a Warchief is allowed to have over the Horde undermines the purpose of the position completely, and it's why we don't have any Warchief now. The writers fucking wrote themselves into a corner where no one they put in that position would really matter, since the Horde (namely anything the Horde Player represents) is shown to continue functioning without one multiple times.