While they don't have the type of "everyone in a room at the end" trope you may be looking for, I can recommend two thrillers from the 80s and 90s that have clever twisty plots that seem inevitable only in retrospect: MASQUERADE with Rob Lowe and Kim Catrall and MALICE with Nicole Kidman and Alec Baldwin. The less said about the plots, the better. For "everyone in a room" there is the MIRROR CRACK'D with Angela Lansbury. It's a bit heavy handed, but Elizabeth Taylor is quite good in it.
Actually, with the success of KNIVES OUT and MARE OF EASTTOWN, I think whodunits are having a comeback, especially on streaming. I think BIG LITTLE LIES w. Reese Witherspoon and Nicole Kidman started it. There's usually a nude dead body (female) in the beginning. Then one hour of community life. Then the body is discovered. The rest of the show concentrates on how the community's secrets about bound up in the killing.