Per Whitebeard, the final war is after the One Piece has been found.
Your take is contradicted by the manga, lol.
Power has nothing to do with it. As you said yourself, BB doesn't represent 800 years of tyranny and oppression.
Blackbeard:
- Didn't destroy Ohara
- Has no connection to Joy Boy
- Has no connection to Luffy's real dream
- Isn't responsible for mass slavery
- Didn't kill Cobra
- Is not the person Roger was waiting for
Blackbeard is just another late game antagonist. He ain't the big bad, folks should get over it and move on.