As I've aged, my interest in competitive multiplayer games has waned. I find that I have no interest in fighting other players online, that I don't really care about the score I get, and that having those things present in a game tends to pair me up with players I'd rather not play with…
Yup, we've played every Borderlands game, It Takes Two, Palworld, Rotwood, PlateUp, LEGO Harry Potter, Deep Rock Galactic, Outward, Stardew Valley, Cult of the Lamb, Sea of Thieves, Baldur's Gate 3, Grounded, Don't Starve Together.... We also play other 'competitive' games co-op against bots, like in Beyond All Reason, Marvel Rivals, Overwatch, and Predecessor. I could go on but I could list games for a while. Definitely always looking for new ones though.
Sure you can play doom 1 and 2 campaigns in co-op. No need for modding. You don't even need a network card. Just buy a cable to connect both serial-ports on the PCs.
That was my first co-op experience and it still one of the best I've ever had.
Our throats hurt from laughing when playing "Chained Together". It's short and cheap. We're happy we picked easy mode for the first play through since that's already quite challenging