i thought it was a common transmigration

It might not be a common one. Maybe it has some unique elements that made you think so.

Yes, many people think it is a common isekai story as it follows some typical tropes and themes of the genre.

The expression "at that time, it was just ordinary" had different meanings in different situations. From the perspective of poetry, it came from Nalan Xingde's "Huanxi Sand." An Yiru extracted the essence of Nalan Xingde's "Drinking Water Ci" from his collection of classical poetry appreciation,"At that time, it was just ordinary." She interpreted the background, style, and character mentality of that era in connection with the love and hatred between men and women. However, the work was suspected of plagiarism. From the perspective of prose creation, Gong Zhuo's lyric prose "At that time, it was just ordinary" described the ordinary circumstances of ordinary people in his memory, showing detailed character descriptions, delicate emotions and philosophical inspiration. Ordinary things settled his thoughts on life and emotions. In daily life, the experiences shared by many people also reflected the meaning of this expression, such as the warm scene of a mother holding a sweater and a fried dough twist standing at the school gate when it snowed in the second grade of elementary school, the leisure of Shandong netizens waiting for results after the college entrance examination, and the joy of knowing that they were admitted to Shanghai Jiao Tong University. At that time, they only felt ordinary, but later they could find something unusual. In short," at that time, it was just ordinary " expressed the feeling that people felt ordinary when they experienced it, but as time passed, they realized that the past had a special meaning when they looked back. The novel,"The Morality of the Past", is equally exciting. Everyone is welcome to click and read it!

Yes, it's quite popular. A lot of manga lovers enjoy its unique story and art style.

Yes, in some philosophical traditions. Idealism, for example, holds that the world is a mental construct, which is somewhat related to the idea that the world is a fiction.