My hypothesis is that not all tasks in a software project require the same level of skill or domain expertise. Context: I'm the technical cofounder and (currently) sole developer of a tiny company developing SaaS applications. The core of these applications definitely does require my domain expertise. But other things, like the purchase UI and account administration, just require one or more programmers with adequate skill and a strong, reliable work ethic to deliver (and maintain!) good enough implementations. Perhaps this suggests a two-language approach for such applications, with the domain-specific core being written in a more niche language. But polyglot projects bring their own complexity that makes it harder to eventually hand off maintenance.
A lot of the "lets just hire lots of grunts" mentality implies someone is going to do a lot of the other work - talking to users, documenting requirements, creating well specified dev tickets, implement SDLC tooling, integrate with SRE, create guard rails, do documentation, testing, code reviews, style guides, etc.
Which is to say - most of the stuff you expect a senior to just be able to do as part of their job while also writing better code.
A large enough org may be able to offload much of those tasks to dedicated people and/or teams. Similarly a mature enough platform could have lots of BAU dev that can go to grunts because the basic infrastructure already exists and the workflows are well known with good tooling.
So it really depends on organizational size & maturity if its a good trade.