Here's some feedback:
-can pretty easily see that these eyes are just squares. Either push em back in the darkness or lower the lighting so the dark reaches lower to cover them up.
-this is very pretty
-why is the monkeynaught locker here? Doesn't make any sense with the map theme or location
-this sight line looks problematic
-invisible walls make me sad, and this is a REALLY big one. Give me a reason why I can't go through this massive open doorway, don't just say I can't.
-the colored fog in this map is a neat idea but feels too prominent. Doesn't fit the TF2 art style at all imo.
-z fighting on these pillars
-I know no one will really notice this but the fact that the wheels don't line up with track bothers me on a primordial level.
-considering how nice other arches in this map, let alone this area are, these lil ones could use some more angles.
-can get stuck in this props
-misaligned texture
-I feel like you could do something like lakeside/Egypt for these exits in the crypt to fit the theme better. Just having roll up garage doors down here doesn't make a ton of sense thematiclly.
-reverting to normal size in this alcove after getting the spell that shrinks you causes players to die.
-what in the world is going on here? Why is a dump truck pulling a train car with a container on it? Is it supposed to be an attempt at a semi truck or something? If so, FGD5's made some nice semi truck models that would make more sense. If not, this still doesn't make sense.
-these pickups could use something on the ground to let people know they spawn here
-clip these pillars
-Did I mention invisible walls make me sad? Upward does this same kind of thing in blu's first spawn but gives a reason why players can't go that way while this doesn't.
-sometimes the spells drac drops fall out sideways. Maybe try something like phys_keepupright to keep them upright.
-I feel like these lil windows need to go deeper if they are going to be straight black in the back.
-minor prop clipping
-love this sewer level. Reminds me of Thief.
-sometimes when I jump while going down this hallway, I get caught up on the ceiling pipes and it fully stops my momentum.
-either clip the board or remove collision by making them a func_brush
-really like all the vertical detailing in this map
-the ceiling here is already really low, this pipe just exaggerates the issue.
-the dirt stopping so directly on the edge here looks odd
-I really, really dislike this and the other grungy textures throughout the map. Grungy stuff can be difficult to make look right in TF2 and all of this really does not fit the art style at all. With how much these textures are used throughout the map, I'd highly suggest taking another crack at them to make them fit more.
-why do these windows reflect green when there isn't any green around them?
-there's little indication that this is a one way door nor which side causes it to open. Some better indication with signage or...something would be good.
-you use this shelf prop a fair amount in this map and I don't think that's really a good thing. Since it lacks any kind of variation in skins or prop placement, having so many clones are very obvious.
-oh hey, more invisible walls.
-There aren't any textures or anything inside Drac's mouth and lets me see all the way through the model.
-There's nothing to indicate what in blu's first spawn is the spawn room and what isn't. Since the respawnroom entity is only in that room on the left, that means changing class anywhere else in this area kills the player. I was rather caught off guard when that happened. What makes it worse is that the resupply cabinet location makes me think the whole area is the actual respawn room, when it's not.
-this map has a lot of harsh colored lighting which, while neat, leads to most of it not looking very TF2 like. I'd suggest toning it down some. Not removing it cause it is neat, just tone it down so it looks more like a TF2 map.
-the metal sheet here clips through all kinds of stuff
-The areas on the sides of this train car look large enough to walk down, but I can't due to more invisible walls. 2fort has something kind of like this with it's train but boards up the front of it so players don't try to go past it. I'd suggest something similar here.
-I like the look of this area. The floor texture is a bit too grungy in my opinion but the rest looks great.
-I really like the strewn about train cars. Helps get that "abandoned" feeling across. Like this place hasn't operated in a very long time.
-gate clips through the tracks
-why do I die when I capture a point? There's no real indication nor reason for it
-can't help but feel like the rectangles on this gate should be signs
-don't know what all can be done about this, but it would make more sense for Drac's jar to be vertically on a players back, like a backpack, opposed to horizontal.
-the ceiling here is already low, the door frame only makes it worse
-why the little drop down here? It needlessly hinders movement for anyone wanting to go back up.
Overall the map has some neat ideas. I'm not a big fan of invade CTF and many of the areas feel a bit cramped but I doubt that's something you'd be interested in improving at this point in development. The main thing about the map, to me, is all the harsh colored lighting and fog. While I agree that it looks neat it's just too much. It causes the map to feel like it's trying to be a different game. While TF2's artstyle has wavered over the years from the purity it had on release, this is just too much in my opinion.
Anyway I hope some of this helps someway. Best of luck