There is a massive difference between 10 years of experience and 1 year of experience repeated 10 times. That is why some veterans still call themselves mid-level—they have the humility to see how deep the rabbit hole goes. True seniority is defined by how much you multiply the output of the people around you. If you are a coding wizard but a bottleneck for your team because you don't mentor or document, you aren't a senior engineer; you are just a highly productive individual contributor.