I think part of the reason you're running into friction here is because you keep insisting your idea is the best and only way forward without any sort of historical context or understanding for why nobody is going to support this plan.
Case in point - building a new bridge over the Mississippi from St. Paul to the airport was a cost so insurmountable that the Riverview Corridor plan twisted itself into pretzels trying to design a route that could reuse the existing MN-5 bridge, and ultimately died the second that the Metropolitan Airports Council looked at the plans and said "Absolutely not."
And that wasn't ancient history or anything. That played out in the last year. You can also look at how the Midtown Greenway's extension to Saint Paul hinges almost entirely on the abandonment and reuse of the Short Line Bridge, because it was determined the political fight with environmental groups over the construction of the new span would be almost as difficult as obtaining the funding to build a bike bridge over the Mississippi.
And those are just the challenges of a theoretical Mississippi River bridge in general. In specific to surface a subway near Downtown to cross the river on a bridge, what part of the parkland are we going to be building a span over, or replace with a tunnel portal? How's that going to go over with everyone's favorite transit haters, the Minneapolis Park Board? How many millions will be spent on plans that get replanned, that get rejected, that end up getting litigated for years by third party groups that hope if they just throw enough money at the issue and gum it up in the courts for a few decades, it'll die on the vine?
It's one thing to not know the historical background of every transit decision made in the metro, but to be obsessed with the minutia of the average ride speed of one route, and to hand waive away the incredible political and engineering challenges of your preferred route just makes it difficult to take you seriously.