Time in the market is not good by itself, but can be a proxy for leveling. Someone could have 15 years of repeating 1-year experience and be a junior dev. Another could be out of school by 1 year and show tremendous potential and have shipped some great stuff and quickly fill a mid-level position. But time in the market is definitely a consideration. Not the most important, but, for sure, on the radar.
For a normal person, it will take time to develop expertise. Time for exposure to novel problems and time leveraged for (the opportunity of) growth.
After you get into an organization, you can level up quickly depending, to a degree, on the speed of execution. I also agree with you that it is uninteresting to gauge leveling based on code style, dependency count, and/or a favorite framework. However, discussions around those can lead to a better understanding of someones professional maturity.