The present perfect tense is often used to express a life experience, which occurred in the past but which usually is relevant to the current topic of conversation. So it's not uncommon to refer to past work experience to indicate that you either don't do that now, or that the previous experience is pertinent to the present.
I've worked as an English teacher in Japan.
I would use the present perfect tense to express that I have this experience, because for some reason the experience itself is relevant to the current conversation. If instead I wanted to talk about the experience without implying any relationship to the present, I would use the simple past:
I worked as an English teacher in Japan during the mid- 1990s.
Note that, as you say, the present perfect tense strongly implies that this is a past experience which has not continued to the present moment. So you would only use this tense if you understand the nuance, for example in a job interview:
A: "Do you have an experience teaching English?"
B: "Yes, I have taught English in a number of countries around the world."
A: "But you are not teaching now?"
B: "No, I currently work in school administration."
To indicate the experience is ongoing, use the present perfect continuous:
I have been teaching English, in various countries around the world, since the mid-1990s.