No, Sirenia is not a goth band, because they play Symphonic/Gothic Metal, while goth music consists of Gothic Rock and its derived genres, like Deathrock, Darkwave, Ethereal Wave, and Coldwave.

However, their music does show some goth influences and could be considered adjacent to the goth scene.

It is important to note that while this band is not goth, its members did make goth music as part of acts like Elusive.

If you want to dive into the goth music scene, some of the bands that might appeal to you if you enjoy Sirenia are Dead Can Dance, Fields Of The Nephilim, and Mors Syphilitica.