This game is undoubtedly an excellent RPG, and its quality can be seen from the ratings of the major ** and the 87% positive rating on Steam. However, there seems to be some kind of indescribable gap between it and Dark Souls 1 and 3, which is not huge, but it is enough to make people feel the subtle distance between it and the "gods". This difference in quality is not the main reason why it was excluded from the Souls series.
The core reason why Dark Souls 2 was marginalized is that its producer was not Hidetaka Miyazaki, the founder of the Souls series. FS fans are well known for their fondness for Hidetaka Miyazaki's unique personal style, and their loyalty to the game is extremely high. From Demon's Souls to Dark Souls 1, to Bloodborne Curse and last year's wolf, Hidetaka Miyazaki's works are always full of what fans call "soul flavor". And Dark Souls 2, which Tanimura is in charge of, naturally seems out of place.
Let's take a look at the background and plot development of the Dark Souls trilogy, which is also known as "Soulology". Dark Souls 1 is set in Rodland, while Dark Souls 3 is set in Lothric, and there is a strong connection between the two. From the opening animation to the countless details in the game, a tribute to the first installment can be found. Although Dark Souls 2 is geographically and plot-related to the first part, the connection is weaker in comparison. It is more about the relationship between people than the entanglement between gods and people.
Although there are also many characters, equipment, and techniques in Dark Souls 2 that have played an important role in subsequent works, overall, it seems that it can stand on its own throughout the trilogy without affecting the coherence of the first and third episodes. That's why many players feel a story break when they first experience Dark Souls 2 and leave it out as a result.
Personally, I highly appreciate the quality of Dark Souls 2 and its place in the plot of the series. A lot of plots that could not be explained in the third work, found the answer in the second part. Although Dark Souls 2 may have been overlooked by the general public and some followers, true fans of the series and soul-science fans will not easily abandon it. I hope that everyone can reduce the rejection, not too much to praise or belittle a certain work, but to enjoy the fun brought by the art of the game more, to experience the unique charm of Dark Souls 2.