Yeah, I'm giving my seal of approval to Cultic as well.
For one thing, the presentation, art direction, use of sound effects and music is incredible, moreso when you realize it was all done by one guy.
The game oftentimes effortlessly switches from blood-pumping action, to horror, to a period of downtime exploration. Movement of the character is very good, the weapon all feel meaty and pack a punch, all are useful (moreso when upgraded) and the enemy designs are on point.
Unlike, say, Ion Fury, it's easy to identify enemies on the map, even from far away - as Civvie said, how easy it is to identify enemies is praiseworthy, especially considering how pixelated the graphics are.
The maps themselves are great, and many are very large and open-ended, allowing you to pick and choose your fights, and how you want to approach them, as well as giving you non-mandatory points of interest to explore. My favorite map by far has to be the mining town since it has all these sheds and buildings you can go into to find items and secrets, on top of the great atmosphere provided by the sound effects. I especially like how restrained Cultic is with the music, usually letting the ambient sound do the work, and only introducing a track to compliment a specific setpiece or encounter.
Lengthwise it took me about 15 hours total to get all the achievements, find all the secrets, "complete" the wave-mode arena, finish the game twice (once on Very Hard, the second time on Extreme).
Some downsides would be the limited number of enemy types (it's mostly humanoids in robes of different colors), problems with telling apart cultists with pistols and machineguns, or hatchets and grenade launchers, the fact fire (lanterns, molotovs, flamethrower) largely trivialize the tankier enemies, overlap in the arsenal (pistol and STEN, rifle and FG-42), some weapons needing to be upgraded before they can be useful (shotgun especially needs the upgrades to speed-up reload and tighten the spread of the pellets) and some maps being hit and miss.
Another criticism is that the game is far too generous with ammo and health pickups. Until I went through the game on Extreme I never really ran out of ammo or health, but that could also be down to my more conservative playstyle, since I liked to snipe enemies from far away and then begin my assault by saturating the area with dynamite, which tended to cut down on the enemy numbers significantly.
On the topic of maps, I remember disliking the catacombs since I thought the map didn't play to Cultics' strengths (Jenkem liked it though, so it may just be subjective), being more reminiscent of something you'd find in Blood, but it and the mines to a lesser degree are the low points of the whole campaign, and the subsequent maps more than make up for it.
Also, again, this whole game was made by one guy, and it one of the best, and certainly my favorite, among the "boomer shooter" games.
