I would argue that aircraft are massively inefficient. Lets just look at the biggest cause, pilots. When flying the aircraft has to deal with cruse and takeoff

I would argue that aircraft are massively inefficient. Lets just look at the biggest cause, pilots. When flying the aircraft has to deal with cruse and takeoff and landing. Basically, the less you have to re-work the aircraft for takeoff/landing the more you can optimize it for cruse. Looking at just one thing, flaps, it becomes obvious how much aircraft could be improved by radical changes. When taking off, flaps are set much less aggressively than when landing. This is because most of the additional lift and subsequent reduction in stall speed, come with just a little flap extension. In landing however the flaps are extended considerably more. This is not for stall issues, but just so the pilots can see the runway. By increasing the flaps we are increasing the angle of attack of the aircraft and that allows the pilots to drop the nose, so they can see the numbers better. Land flaps are a huge change to the configuration of the aircraft and require a lot of structural changes to happen, just so pilots can see. Those changes cost cruse performance massively. There are many other things like this in air frame design, materials, etc. Just look at the experimental aircraft world compared to certified designs. The differences in performance are massive but they don't come to market because the industry is so stuck in its rut.