@Ribath
That's really stretching it.
The usual premise of isekai is that the very supposedly relatable main character came from another world and would bring his insight, knowledge, and skills that may bring about change in the new world.
The isekai setting is also a convenient way to easily narrate the fantasy setting through the eyes of the main character without having to consider how the main character sits in the world - the main character does not have the knowledge of the flora, fauna, culture, and technology of the new world, so there is no way for him to act in an unexpected way. It's also easier to relate to the surprise and wonderment of the main character, who came from the same world as ours.
It just so happens that the media in the isekai genre is saturated with a harem premise, since that's the sort of thing that's popular among male authors and readers. Sometimes, the isekai aspect becomes negligible in some of the stories that it may as well be a plain old fantasy setting. However, despite all that, a fantasy setting with no other-world/original world aspect to it is strictly not an isekai.
That said, if jumping into a new workplace as a graduate was enough to be an isekai, then New Game should be an isekai for you too.