The most avant-garde Doom will ever get. Obviously not a WAD for everyone, the core target for such a mod is mainly people who are in video game glitches, corruptions and to some extent, creepypastas (whether that love is ironic or not). Nothing works as it is supposed to. You can hardly understand most of the things that are happening to you. Some of the custom monsters (like the hitscanning corrupted pinky) will put you on edge and keep you paranoid about the ruleset of the game.
The aesthetic of lilith.pk3 is one of a kind, horribly mangling the rendering engine of old ZDoom beyond belief to disform sprites, textures, text and even sound effects. The end result makes close to no sense, your Doom marine sprite is heavily dislocated and looks more like one of those creatures from Alien than a human being and the list goes on and on. The confused looks obviously doesn't always make for clean or concise gameplay, especially in later levels which crank the confusion up to eleven and manipulate the level geometry to do things you thought weren't possible in the game. Even basic things like crushers, slime pits or a turnstile look horribly out of shape and makes the player uncomfortable.
This is essentially what lilith boils down to: an unfamilarity to something we thought we knew by heart, a rising sense of uncomfort as the level design makes less and less sense and offering the player a new perspective on what Doom is. Don't play lilith expecting top-notch Doom gameplay, but play it for the one of a kind experience it offers you. For the better and for the worse, there are no WADs like lilith anywhere and there will never be.
I think that the combination between shotgun and chaingun combat, and the hitscanner shootouts this WAD offers are really fun and engaging. Pinky Demons are placed in areas where they're not frustrating, (The opposite being something I see very often, nice work Romero :P.) My only issue with this WAD is that one or two of the secrets, specifically those found in the darkened tech room, are sort of esoteric. The one where you have to jump from a platform isn't the worst, but the one for the Mega-Armour is annoying and in my opinion, unfair to find.
Despite these small issues, I think that Phobos Mission Control is an excellent and exciting level to run through, and I applaud Romero for returning to the Doom Community to make new levels.