This is a clear case of projection.
I'm not invested in any particular outcome in the narrative, but you are, and you seem to think you can will certain outcomes if you just believe hard enough. It doesn't work that way.
There is no truth to any of this, beside your clear lack of imagination. You keep going back to this well as if you know what's ahead of us in the story. You don't know.
They're calling it the clearest case of project in 2026.
Blackbeard's intentions are Marineford happened and Whitebeard died. They very much matter.
Not a single thing you've raised presents an actual obstacle to his being the final villain. What the world needs has no bearing on what Blackbeard wants to impose on it - assuming he even wants to perpetuate the WG in its present form.
The only thing that matters is Blackbeard's desire and ability to usurp Imu's throne. Oda's been writing towards that becoming a reality for damn near 30 years, with each revelation about him making that clearer.
Your issue is that you've lost track of the wider context surrounding Blackbeard. As a result of that, you've lost sight of the work Oda has put in, like his history with Shanks, his Davy clan heritage, WB's final words, the nature of his Yami Yami DF, his ability to consume multiple Devil Fruit, and the fact he doesn't sleep, which has particular literary weight in a series that puts so much emphasis on dreams.
What's funny about you projecting on me that I have some rooted investment in Blackbeard being the final villain is that the one with that rooted investment is the author of this series, who I remind you again, has been building this villainous character 30 years.