Senior engineer is a "terminal" position at most companies, and certainly is not a bad spot. Only around 15-18% of engineers were above that at my last big tech company if I remember correctly.
Senior is the last IC level where you can pretty much exclusively focus on the technical work, in most cases. You can be very successful doing this! Staff and above roles can vary widely, but most of the time you're expected to have a multiplying effect on the team, which requires a lot more soft skills.
If a company has too many engineers above senior you run into a problem where everyone is looking for impact, but no one is doing the actual work!
Senior is the last IC level where you can pretty much exclusively focus on the technical work, in most cases. You can be very successful doing this! Staff and above roles can vary widely, but most of the time you're expected to have a multiplying effect on the team, which requires a lot more soft skills.
If a company has too many engineers above senior you run into a problem where everyone is looking for impact, but no one is doing the actual work!