Alright, I feel that I got the most of this game within my ~6hours of gametime. Let's see why exactly I clicked Not Recommended button.

Quick summary

Pros:
-Fun, fast gameplay with some skill involved
-Many heroes to play, all of them have distinctly different abilities
-Loot system provides basic customization

Cons:
-Horrible UI and overall lack of critical information
-Poor dificulty curve, areas 1,2 are perfect, 3 is hard as hell and 4,5 are just a breeze. Same with area bosses
-Certain areas have extremely repetative gameplay, spawn points allow for easy abuse
-Almost no replayability aside from trying new hero

Breakdown

Gameplay:
Wave based action with some loot and skill progression. 5 Areas, 5 bosses. Many different heroes to play. Simple and elegant.

Loot:
You have 5 slots that you can equip dropped items to, there are few stats and around 10 Special Abilities attached to the items themselves. Not much creativity but does the job

Classes:
Truly outstanding feature of this game, all classes feel different, have different tactics and MIGHT have a few distinct builds.

Hero skills:
You have 4 skills (aside from 1 hero who has 7) and you can level them up. This will be very familiar to players of Risk Of Rain. 4 skills, 4 button to press. Usually is goes something like - basic attack, special attack, dodge ability and some sort of an ultimate, although it might vary from hero to hero.

UI:
Horrible. Well, maybe close to horrible but still really really bad. When you try to compare pieces of equipment you only see stat comparison that is already on the previous item. Example - if your item has no armor but has cooldown reduction and if the new item has armor and has no cooldown reduction it will just show you +33 armor and will not compare non-existent stats. It is REALLY hard to compare items at a glance and you have to constantly switch from item to item to understand if you want to use one or another. Skills APPARENTLY have two different power levels, 1 is before you put 4 points into it and 1 is after. This is NOT mentioned anywhere and seems like a critical piece of information missing. Some skills SEEM to get new abilities with new power level - life steal, health regen etc , but that is also NOT mentioned anywhere, skill descriptions are only visible in tutorial and do not provide enough information. You have a certain level requirements to upgrade skill beyong certain level, but that is badly represented and the only indicator is that they are not hightlighed during the level-up process.

Movement:
Very floaty, has almost no precision, hard to dodge certain attacks. Hitting flying enemies feels like a roulette as you cannot control angle of attacks

Mobs:
Decent variety, some really cool designs, some (IMHO) horrible decisions on mob power. Area 3 has the most annoying Spearman that is basically harder than any boss of the game

Bosses:
First 2 bosses are AS COOL AS THEY CAN BE! They are fun to fight, unique and present decent challenge. The rest are boring and super-easy to fight. Seems like the developer ran out of creativity\time to polish them

Areas and levels:
Hard to say. Some platfroms, some fires, some nice backgrounds. Nothing special, nothing bad.

Difficulty:
Super-weird. First two levels are nicely balanced and present good challenge. Third Area is just super-hard due to one type of monster who can silence your attacks, slow you down AND teleport to you to punch you. One wrong move and you are dead. Fourth and fifth Areas are easy, I have not died once and never even came close to being in trouble. It seems that the late-game might not be balanced hence the weird difficulty curve

Replayability:
In my opinion - none. Game is around 3 hours per run, by the end I felt tired and bored. Played a bit of horde mode, got even more tired and bored.

Overall:
Nice game, but has very little to offer for the price. I would only recommend to buy it of huge sale, around 2-3 dollars just to try it out

Cheers!