Calantheshaman here is defination isekai

Isekai (Japanese: 異世界, transl. 'different world', 'another world', or 'other world') is a sub-genre of fiction. It includes novels, light novels, films, manga, webtoons, anime, and video games that revolve around a person or people who are transported to and have to survive in another world such as a fantasy world, game world, or parallel universe with or without the possibility of returning to their original world.

notice how it says game world? Yes the survive part is easy in video game ones but still counts.

Isekai translates to another world. It doesn't mean another physical world, summoned to another world, or one way trip to another world, it just means another world. It can be a video game or they can travel back and forth between "our world" and the other world all they want. I don't where the idea that Isekai did not include virtual worlds came from but it is wrong in every sense.