I'm considered a senior engineer by the company I work for and my peers, however it makes me cringe to write or say it. I think it comes across as pretentious.
Labels are a leaky abstraction, genuinely useful for those who don’t (want to) care and know. But useless, maybe harmful, when it comes to difficult problems, conflict and subtle interactions. In these cases we need to recognize that the map is not the territory.
If I meet someone with 8 years of experience that is not confident to tell me they're a senior engineer, I won't hire them.
If I meet someone with 2 years that tells me they're senior. I'll listen to what they say carefully and judge if they can do the job.
Titles are useful labels that compress a lot of info. It's not about how accurate they are, is about trying to differentiate quickly.