This is so true. I work at a fairly small organization (~35 devs). Large enough to see roles form but small enough that I can tangibly see everyone's contributions. I work SRE, so I see lots of code from all the teams and ultimately talk to almost all the devs.
In our impressive enterprise-level codebase (our SaaS product has average annual subscriptions in the range of $1.5M per customer), there are probably 3 developers that wrote 80% of the codebase. I can name them all and call them up. But I said we have 35 devs in the organization. So what do they do? Mostly little things. Flipping a conditional or making a slightly more explicit test case to fix an unexpected edge case we experienced.
Most of these 32 other engineers are solving simple problems, basic refactoring, and so forth. Not too different from the adlib, fill-in-the-blank analogy you provide.
Also, to be clear, it isn't like we hired 3 seniors and expect them to write all the code. These are just groups people fall into naturally.
The reality is most software engineers have only ever done the adlib style work and have built an entire career around never solving any real problems. They know just enough syntax in a language to solve the little problems and with software, there is a near infinite supply of these little problems.
