In many organizations, marketing is just asking customers what they want. E.g. ask a farmer from the turn of the century, they'd have said "I want a horse that pulls harder and eats less oats!"
They'd never have said "I want a tractor!"
It's Engineers that conceive of tractors.
They are the ones by talking to the customers and knowing what they need. They are the ones that know that one engineer has been working on a high power engine, and other on rugged, high traction trailers.
Purely engineering firms fail in the long run as they drift away from what buyers want and chase interesting things because they think they know better.
Marketers coming up with ideas and dictating those ideas to engineers is just wrong
Eh, it's not about purely engineering. Many businesses who are not related to engineering fails exact same reason. They only care about short time growth and loses. Happens all the time.
That being said: you are absolutely right. How quickly the externalities are forgotten.
I haven't run the numbers but I have the impression that "idea people" tend to flounder without a strong technical co-founder. In contrast, technical co-founders can make it on their own, though there may certainly be challenges in doing so. Those roles are also very different in terms of what you can hire in as early employees vs what absolutely has to be a part of the founding team.
Almost everything in a big organization is a team effort, but that doesn't mean you can't tease out the relative contributions of the different parts. And I think you're undervaluing the engineering contribution substantially.
Lots of successful businesses have been founded and run by founders with no formal engineering training. They all need some level of business knowledge, but that can to some degree be learnt on the job.
Then they throw it to engineering and either take the credit or shift the blame.
Sales, Marketing, and GTM are absolutely generating 100x - 1000x their salary if they take sole ownership of a project like you are doing.
SWEs are good are solving problems, but other people determine which problems to pay attention to, and how much investment to make in them.