In jobs where skills are common, salaries are lower because pretty much anyone can substitute in to do the work.
I think this is valid for operational works.
but also on the value that the person brings into the job with them. some people do what is needed to be done. Some people do so much more.
Unfortunately, both person would get almost the same salary in many companies.
From my perspective, if current job A pays X and future job B is more valuable to the company, it has to be better rewarded.
In general, there would be a job transfer for the future job B, and the transferred employee from a company to another rewarded better.