From https://promusicianhub.com/what-is-punk-music/
In its most basic definition, Punk music is a manifestation of the rebellious, anti-authority punk subculture that peaked in the second half of the 1970s, primarily in the US and the UK. Not just a music genre, but punk is more of an attitude, a philosophy, and a whole way of being.
Sure it doesn't sound like punk music, but they sure as hell ripped a massive middle finger at authority.
Punk isn't a genre, it's a lifestyle. Somewhere in the 90s people, including the artists themselves, mistook it only as a musical genre.
The 1975 is punk imo, even though they dont fit the genre.
They're pop or maybe alternative. Definitely not punk. And kissing a fellow band member doesn't make you a punk