As I've gotten older and have less time to devote to Doom thanks to my job, my own tastes in what I play have changed. These are some of the things I look for:
-Number of maps: I love lengthy Doom adventures so I'm always looking for megawads. As long as a mapset has at least 6 maps in it, I'm willing to give it a shot (though there are some map(set)s with less maps that are impressive enough for me to make an exception).
-Mod compatibility: I consider myself a gameplay mod enthusiast so anything that lets me plug in mods is very much welcomed. As such, I'm really fickle about how Dehacked is used. If it's used for map names, that's fine. If it's used to replace the SS Nazi, Keen, or unused assets to implement new monsters (like the dead Lost Soul), I can deal with that. If the Dehacked actually touches the monsters in any way and/or modifies the weapons, I'll most likely skip it. There are exceptions to this, of course (like Avactor. I love what it does with the monsters, I can use weapon mods with it, there are some monster mods I can use with it - namely LegenDoom Lite and Corruption Cards, and the level design is top notch so it gets a pass).
-Continuous playthroughs: I like to be able to carry my arsenal and inventory throughout my entire playthrough of a mapset, only losing it and starting over if I die. If I come across a death exit, I won't hesitate to get around it by invoking IDDQD or using mods that let me get through it unscathed. If a mapset uses ResetInventory, I'll quit and move onto something else that doesn't use it. I don't like the idea of punishing the player for doing well but I realize this is probably a "me" thing.
-Id-like flow: By this I mean killing barons lowers stuff in e1m8, killing arachnatrons and mancubi does the things in map 07, map 15 has a secret exit to map 31 which has a super secret exit to map 32, etc. Essentially anything that plays and flows like an IWAD. Anything that deviates from that flow tends to sour the wad for me. For example, I'm not a big fan of the episode structure used in Doom 2 by Valiant and Eviternity. I'm also not a big fan of map 07 slots doing something beyond killing mancubi and arachnatrons. Examples of this are Valiant's map 07 where you have to keep the Mancubus alive, Interception 2's map 07 where you have to repeatedly kill a Mancubus to lower multiple walls to exit, Slaughtermax's map 07 arachnatron shenanigans, Skulltiverse's map 07 where you have to keep an Arachnatron alive, and the entirety of Dark Scythe (I still don't know why/how monster mods break Boom maps that utilize tag 666/667 outside of map 07 but oh well). Finally, I'm not really a fan of secret exits being in levels other than their intended one. Lunar Catastrophe's secret exits not being on their usually expected levels is an example of this.
Admittedly I'm not really a fan of puzzle maps either and I'm picky about slaughter maps and hot starts. I don't mind slaughter maps and hot starts so long as the player has the gear to deal with it. Therefore, I prefer them to show up in later levels of multilevel WADs. Pistol starting a sizable mob - especially if they start alerted to my presence - is a real motivation deflater.
I know I have strange tastes when it comes to WADs. :V