So many of the great (financial) success stories of our sector are about startups stumbling into an untapped demand, and then running with it for as long as the money lasts. Nobody sets out to build a bridge – they build a 2x4 plank, and then realize that rather a lot of people want to walk on it.

That's a difference between contractors, people, groups, teams, projects, etc. It has nothing to do with the "disciple of engineering" software or otherwise.

I've seen shitty mechanical engineering projects, but hey, it was cheap, so I don't blame the customer! (We're fighting the shit someone churned out from the software side.)

No one expects to go to a mechanical engineer and ask for a new car, 4 wheels, blue color, 200 horsepower, and a week later "could you just make it 8 wheeled, thanks" and a week later "could you also make it so it'll be fast even when run on a mix of vomit and vodka", and so on, yet it's the norm in software.

And we somehow compare it to bridges, because a lot of software is "critical infrastructure".

Put the two together, and it's no surprise it seems that software engineering is not mature enough.

It simply means some kid (or a team of expensive consultants), who knew nothing about long term risks of the combination of attention fatigue and shitty UX, said yes. Lowest bidder and all that too. Or because this was mission critical it never occurred to the procurers that a UX guy/gal should look at it.