It’s a garbage word because it’s too vague to be meaningful. People use it to mean anything from “not a newbie” to “the best in the world.”
You can’t call yourself an expert without sounding like a tool. People assume you think you’re the best even when you’re just claiming to be a non-newbie.
And you may call someone else an expert as a flattering way of saying they’re not a newbie. But they hear “expert” and think “oh no, they think I’m the best and I’m not at all.” That’s a healthy spoonful of imposter syndrome from a single word.
Stop saying “expert” and start saying what you mean. If you’re looking for the best in the world, say that. If you’re looking for a non-newbie, say that.