A closed crime scene with a finite number of suspects, such as a country manor house with a group of weekend guests. Or a similar setup. Sleuth may be amateur, like Miss Marple, though not necessarily. Inspector Alleyn wasn't exactly an amateur. A minimum of blood, yes.
I don't know who writes them these days---but they're still out there for readers who want a little caper, an amusement for a long weekend at the beach, or a plane trip. Nothing wrong with that.
Of course even writers who don't write cozies can still use some of those elements from time to time. I can think of several offhand, including P.D. James.
Admittedly I don't read many cozies so I have no idea how may good ones are being written these days, but Louise Penney's novels are very good and would likely qualify - they take place in a small village with a limited number of suspects and usually the killer and the victim knew each other.