Aerodynamically the wetted area that generates drag without lift is undesirable. You need a wing generate lift, but everything else is there for something else like stability, handling, payload etc.

In conventional "tailplane" configuration the fuselage and tail are just providing drag and almost no lift (tail has little wings 'upside down' generating negative lift and trim drag). If you have canard or some more exotic wing configuration you can have all wings generating lift but there is still drag from the body. In clean flying wing, there is nothing else except the lift producing wing.

Swept wing in the Flying-V is clever way to get a optimal thickness-to-chord while keeping the total surface area in check.

(If I understand correctly, what is required is that its angle of attack is lower than the one of the main wing, or equivalently (if the wings have the same shape) its wing loading.)

See section 6.1 here, for example:

http://www.av8n.com/how/htm/aoastab.html#sec-basic-stability

But as the source you provides say: "indeed most aircraft operate with negative tail lift most of the time."

In practice all commercial aircraft have the center of mass so much forward that require negative lift for stability. If you look at the cross section of the horizontal stabilizer, it's like wing upside down.

See also:

https://aviation.stackexchange.com/questions/34963/is-a380s-...

https://aviation.stackexchange.com/questions/30400/will-opti...

Note 1: Boeing once toyed with a blended wing-body, a sort of flying wing, to produce dramatically better aerodynamics and fuel efficiency. Passengers would have sat in a wide cabin, rather like a small amphitheater. But tests with a mock-up produced such a negative reaction that the company dropped the technology, except for military refueling aircraft.

Although, I found an article from 2018 [1], quoting a Boeing VP of Product Development and Future Airplane Development, which basically says a blended wing design for commercial passenger aviation is unlikely because the required minimum height for passenger loading implies a minimum width that is quite large, and may not be very compatible with existing airports.

[1] https://leehamnews.com/2018/04/03/dont-look-for-commercial-b...

The Global Hawk has a wingspan over 50% as long as an A350, yet it weighs 1/10th as much. There is no comparison.

I agree that there is no comparison - in the sense that the two cannot be compared that way. For example: A childhood toy of mine (a compressed-air plane) needs a wingspan 1% as long as an A350, yet it only weighs 1/1,000,000th as much - and can still only stay airborne for 30 seconds!

This discussion [1] on the different most-aerodynamic plane shapes is fairly interesting, and certainly doesn't confirm the person above who claimed that a flying wing is the most aerodynamic shape.

[1] https://aviation.stackexchange.com/questions/17119/what-is-t...

Depends on the use case: for a feeder aircraft (regional to international airport) load, range and speed isn't terribly important, but fuel economy still is, for economical reasons (and for ecological reasons, which translate into economical by making the tickets an easier sell to a climate-aware population). In well developed regions, the main draw of feeder planes over ground transportation is not travel speed, but the convenience and piece of mind of checking in at your home airport.

Since a lot of regional (or effectively regional) airports are wildly overbuilt in hopes of attracting bigger connections there could be a market for a plane that fills the available width with a modern high aspect ratio wing to max out efficiency for small loads. If new aircraft designs weren't prohibitively expensive or fuel would be much more expensive this kind of plane would exist. Basically, put the wing of a Global Hawk on an ERJ-145.