It seems that you do not have a complete understanding of music style.
Aesthetically speaking, Gothic is an artistic classification that tends to be dark and pathos.
So Gothic music mostly interprets sad, wet and cold situations in slow speed.
There are two types of Goth music styles: Goth Rock and Goth Metal. Namely goth and goth metal.
The best way to understand it is to listen to it yourself. I will recommend a few bands to you in each of these two categories.
Goth Rock: Lacrimosa and Bauhaus. I won’t introduce Lacrimosa, a well-known European tour group. Bauhaus can be said to be the godfather of gothic rock. They used harsh guitar chords and cold and ethereal synthesizers to create a minimalist, aloof and dark representative style in post-punk rock. In the band's short history, they have explored almost all possibilities in the music they pursue: in their bleak and bleak overall musical atmosphere you can feel the complexity of glam rock, experimental electronic rock, funk and even heavy metal. ingredients. While their followers stagnated helplessly in the face of trends, the styles they created have been very successful and have survived to this day.
Goth Metal: Theater of Tragedy and Nightwish. TOT is the creator of gothic metal, and NW is the most popular and most listened to gold band today. Recommend TOT's "A Hamlet for a slothful vassal" album. You will understand more after listening.
From the perspective of a professional musician, the Portishead band should be classified as electronic and trip-hop music, and has nothing to do with goth. And that song has nothing to do with goth.