I'd say almost all engineering will be in demand - except petroleum engineering. What I'd focus on is what tools you think will be important 10 years down the line. With that said I'd suggest 2 things. Firstly I would learn tangential skills related to your discipline. ex. welding & machining if you're a M.E., construction technology if a C.E., etc. Secondly you need to earn to program and not just the shitty 1 semester "Intro to Java" class for the degree requirement. Basic comp sci skills is going to be the new calculus for engineering going forward.

Oh and don't ignore your soft skills. Proper report and memo writing along with public speaking will get you further then you can imagine.

I'd say it boils down to our technology is significantly more advanced then the layperson believes, along with no one notices the incremental advances until it's combined into a greater whole. AI (expert systems really) and aerospace have lineages going back decades.

Unlikely. Some of the past mental feats that are attributed to "see, we're getting dumber" are based on training instead of native capability. For example, memory training was important before widespread literacy, but now survives as a competitive sport and taxi drivers. Both the drivers and competitors make use of the part of the brain responsible for navigation and neuroscientists have actually proven that that region develops with use. (read up on the Method of Loci for more)

If anything I see our mental potential becoming "flabby" due to laziness and a lack of mental exercise - or worse, a devaluing of these skills because its not a "real job". Like ditch digging.

The simplest reason is that it doesn't necessarily lead to cutting back on plastic production and could even be used as an excuse to boost production of petroleum based plastics instead of plant based plastics.

Secondary is that with the glut of information and social media easily available to the public, there are legions of "experts" on topics where their only qualification is they read an opinion piece on a Facebook post. The heavy criticism of nuclear energy while ignoring "where do they get the rare metals?" for renewables is a good example. There is no quick fix to the problems currently facing humanity and sadly there will be those who cannot recognize the intermediate steps we must take to ween ourselves off our destructive habits.

There's a technique called "Thermal Depolymerization" that can turn plastic (and organic waste) back into a crude oil which can then be processed into fuel oil or new plastics. But as soon as people hear that it makes oil you'll hear some autistic shrieking from some activist and the idea - at least for recycling, gets shelved. It may not be the best solution, but it at least takes care of part of the problem.