[ryanong]

I would call it more of a plateau than stagnation. The senior title is a pretty beautiful spot, well paid and always more to learn but the value to the company is limited to the work you get done. You may be able to get it done faster and better than anyone else, but there are diminishing returns on speed and quality of an individual. I miss being a senior sometimes. Being able to go heads down and pair with someone all day on a problem was a great feeling, but I enjoy how much I help my coworkers/friends.

[solipsism]

I agree with what you have to say about it being a plateau... but what are these companies where a senior engineer's impact is limited to the work they get done as an individual?

Part of the definition of "senior", everywhere I've read it, is that your impact has started to spread outside yourself and to the team level. If you're a "strong IC", you're not a senior, in my reckoning. You're a senior when you're pulling up those around you.