[olliej]

Seniority doesn't mean "senior", it's a product of expertise. Obviously there is a strong age correlation because generally going up seniority ladder is going to correlate with time at company, and domain knowledge/expertise is going to be correlated with time spent work in that field.

But I know plenty of people my age (my vintage? :D) with higher and lower seniority, similarly I know people older, and people with more time at the company in the industry with substantially lower seniority, and vice versa.

But also the companies I've worked at (FAANGs, so obviously large) don't treat "seniority" at the IC level as giving some kind of priority over lower seniority ICs. Obviously seniority factors into "how reasonable/accurate is their opinion" but that has never, in my experience, been a blanket override of lower "seniority".

The primary real difference is compensation, which is why companies like to get rid of senior engineers. I assume for a competent company they're doing a trade off "how much do they cost vs. how much value do they add", but obviously where we see this is always poorly managed "get rid of all the expensive people, WCGW" policies.