I don't think it's meaningless even if it's not completely codified. I use the term senior as a way to distinguish someone that's competent enough and knowledgeable enough about the environment to direct technical initiatives like architectural decisions that will be acted upon by other developers, and be a consistent go-to resource for others for questions either about the environment or coding. When I you l was a chef, it was a little more cut-and-dried because the organization required more of a hierarchy, but there was still the same dichotomy. Lots of young talent could mop the floor with the older cooks — but it was a combination of knowing the environment— eg cuisine, equipment, processes, etc— and knowing how to cook. It wasn't at all unheard of to have a young cook make sous chef over older cooks, effectively becoming the senior, even if they were still asking the older cooks questions about how specific things get done around there.
I agree that it _should_ imply expertise, but it doesn't in practice. It bugs me because start using it as a status thing: "how to think like a senior developer", "listen to me because I'm a senior deveveloper". The title hasn't earned its credentials and it keeps getting used to fake credentials. Instead we should talk about good developers vs. bad ones.
Heck, I know someone who got the title of "senior" on their first job out of a bootcamp. They were credible in the sense that they had worked at other companies before and had a grown-up and dependable demeanor. But they weren't someone I would want to take coding advice from.
I've been lucky in that anywhere I've worked, titles like that came with additional technical responsibilities and were awarded by technical managers who actually had a stake in whether or not people were qualified for them. The youngest company I've worked for started in the early 90s, though, so I've weirdly avoided a lot of the practices born from startup culture over the past couple of decades, and haven't had the chance to get burned by (many of) them. Sort of parallel to your criticism is the "what do I call myself on LinkedIn before I've had any actual job titles" thing, which I really don't care about. I've had a bunch of job titles over the years and I've gotten 'less' descriptive in my 'business card' level title for those sorts of uses— I think it's all up to whoever is doing the hiring to cut through the chaffe, and anything on LinkedIn should be considered marketing fluff anyway. Maybe it's different with ATS job applications and HR people?
