Not all software is made to make money.
There is a more convincing argument that saving time is a motivator in a significant proportion of software either directly or indirectly; but honestly that ugly assumption of monetary motivation in everything of value is quite alienating to some of us - even in something as benign (?) as a discussion here.
Your description of a senior engineer is not a job one person should be doing. If you’re trying to get a senior engineer to figure out how to make something, support it, deploy it, and monetize it, you’re going to get half assed work on every front.
Beyond all that, the ranking of senior should be more company scale specific. A senior engineer at FAANG needs to be able to scale infinity and build things that never break. A senior engineer at a 30 person company needs to build quickly and AB test features rapidly. Ultimately, “software engineer” is far too broad. It doesn’t really embed much knowledge beyond “knows how to code”.
Easy - until some other metric comes along to reliably replace it
It's a useful rule-of-thumb
It's not an absolute, and, had you bothered to read Outliers, you'd know that
But it's more fun to sit back and armchair quarterback others via anecdote, right?
Have worked as both PM and developer and now run my own very small software company
A) two years senior engineer is like one of those consulting companies where everyone in 2 years becomes DIRECTOR
B) In two years most new programmers have not even gotten their heads out of their asses
C) You should refer to Outliers
10,000 hours to master a task
And to that add
10,000 hours to make your first masterpiece
D) Even if you have managed to get 10,000+ hours of coding experience in high school and college and somehow become a very good programmer (which less than 3% of CS grads do)
it will still take you 6 to 10 years to get another 10,000 hours of working on masterpieces and making really good software that you can ship and make money from
E) a title like 'Senior Software Engineer' should be reserved for someone who has MADE and SHIPPED and GENERATED MONEY from a very good piece of software or some software product
F) Personally, I would think any company handing out Senior Software Engineer titles after 2 years is a joke
Between all the places my friends and college mates and I have worked (Microsoft, Google, Amazon, Facebook, Oracle, etc. etc) I can't think of any place that handed out Senior Software Engineer like it was candy
Even very, very good programmers had to EARN IT