There's a vast, vast divide between people who can use Rails and people who can design and build Rails, and an even bigger divide between the people who can use AWS and people who can design and build AWS.

The company in the OP isn't in the business of systems engineering, they're in the business of software integration. I suspect if they were in the business of engineering they'd have a much different view of what it takes to be "senior". Because they'd be able to measure it in terms of lawsuits, audits, and fines rather than in slipped deadlines for web apps.

it's easy to "build a web app in weeks"

The really hard bit is:

Building a web app that can evolve and grow to build a business over several years, eventually with a large team.

And that's where traditional Rails development fails, and we still haven't worked out quite the best way to resolve that.

Medicine you could kill a the patient. Law you could send a innocent man to jail.

Software dev you could do either, if you end up at the right subcontractor at the right time.