Apocalisse - DEMO

This is a prototype of a game and it has one serious flaw: it's not very fun. It's quite boring in fact. I wanted to keep the gameplay minimal, but maybe I overdid it. I wanted to make a multiplayer game, but I think a multiplayer game should still be fun even in SP, and that's not the case.

What could I do to improve it? Or is there no hope and it's better to just keep it as a demo? If you have a few minutes to spare, I'd be more than grateful for your opinion!

This demo was realized with very pixel simple art, mostly made by me; the flames in the ending is from devkidd; fire in the opening and angel spawn effect from CodeManu VFS pack; musics from DavidKBD; screaming people from Dillon Becker under license  CC BY 4.0 (500+ Character Voice Audio Files! by Dillon Becker), and other "minor" sounds effects from various sources. 

Instructions:

Move character with WASD or arrows; use mouse + left click to select options.

Aim with mouse.

Run with shift or left mouse button. Right mouse button to attack. Both running and attacking consume IP (InfernalPower)

Mouse wheel to zoom in or out.

Goal: kill at least 50% of population.

Angels: they make people pray. When praying, people decrease their chance of going to Hell continuously, then die and go to Heaven. You don't want that. But you also don't want angels to become angry at you. They are powerful and can't be killed. They can be stunned, but when you do so, another angel will be spawned in a random location. Angels are also spawned as people get killed. There are 6 types: two colours (stats vary) and 3 different weapons.

Messages: All messages are announced with the same sound too (hey, it's a prototype). So both angel spawns and level ups have the same sound. Choose your power up among 3 randomly chosen by the game. At level 10, you get 3 powe ups. My suggestions: AoE, Max Damage and Speed as much as possible. 

"Allelujas" announce the descent of an angel in a location somewhat close to your, in addition to the standard sound as above.