These days the title "senior engineer" is handed out like candy. Anyone with three years experience is now "Senior" in title. In the US, doctors fresh out of med school have a minimum of three years ahead before they can even begin to practice independently. For programming, and pretty much any other profession, senior doesn't really begin until nearing 10 years of work experience.
At that point, that itch to turn boring problems into interesting problems takes on a different form: What becomes "interesting" is doing things within constraints, including the constraint of staying with existing technology, when it's solving the problem.
10yrs is a very long time in Computer Science. All the engineers I’ve worked with from earlier eras are very influenced by what they started their career with. Heck I’m the same way as I approach my decade threshold.
Title inflation. I speculate based on no evidence other than my own observations that it's because companies aren't willing to pay entry or junior engineers well enough, so lots of them get hired at lowball rates with an implicit understanding that they'll get promoted to senior after 3 years and get the a corresponding pay raise. Either that, or they don't get promoted or a raise, change jobs, and get the senior title by default.
Promotion is absolutely my employer's main retention tool. Many of our senior engineers who leave don't end up with a senior title at their new employer, but they do get a bump in pay.
At that point, that itch to turn boring problems into interesting problems takes on a different form: What becomes "interesting" is doing things within constraints, including the constraint of staying with existing technology, when it's solving the problem.