Hello! So I have been interested in game development for a few years now. But.. I haven't bee able to develop anything as time focusing on School which I still need to do as well as keeping my passion alive for the project is hard, but I think I have a game I am willing to spend time on. Specifically, a game idea.

What I want to give out and eventually develop into a fully fledged game is a Boss Rush game, like Cuphead, with of course some upgrades. There would be 4 classes. These however feed on my obsession with the 4 elements. I imagine it having similar graphics to Dead Cells, and after a few bosses. When your at the end and final boss. You'd have to either face a copy (Singleplayer) or the other player (Multiplayer)

Air would be a mainly fast attacking but average health with mostly ranged attacks.
-Beginning abilities-
-An Air burst, Shotgun like attack sending the enemy back along with dealing above average damage, but has the most cooldown timer
-A simple Air shot, a simple 1 shot of Air.

Earth would be the tank of the 4. High defense with slow attacking and mostly melee attacks
-Beginning abilities-
-A wall type of defense that is the height of the character. It can take at most 5 hits before crumbling, but can be upgraded with spikes and more durability
-Weapon summoning. Instead of a chosen weapon at the beginning. Earth can summon random weapons (Warhammer, Hammer, Broadsword, Greatsword, etc.) that wil break after 2 hits on the boss, but will form another weapon when the tank tries attacking again.

Fire would be the dps. Dealing above average damage with moderate attacking speed but have the lowest health of the group.
-Beginning abilities-
-A flame pillar that lasts for 5 seconds and deals continuous damage with a 55% chance to burn the boss. It can be changed to either Horizontal or Vertical and wouldn't damage the other players
-An ability to enchant your weapon or your friends weapon to deal more damage and give a 10% chance to burn the boss

Water would be the healing of the group, with average everything but slightly more health than average.
-A whirlpool like attack that can stun the boss for 10 seconds after it is used but during this time. Water and the other teammate are healed for 25% of their overall health which can be changed to be 50% or 75% or all the way up to 95% of their overall health.
-A healing pool that as long as Water doesn't leave it or is attack for more than 100 damage then it will slowly heal the other player 5 or 10% every 20 - 25 seconds

That is what I have so far but I plan on adding more abilities and upgrades when or if I am able to work on the game. I just wanted to get a wealth of opinions and feedback on my idea and if it is worth it or not.

Depends on the direction you want to go in.  How is the game going to be visually executed?  Cuphead had the retro sytle combined with the solid gameplay to give it a unique feel.  Is it going to lean towards platforming/run and gun style like cuphead, or a castlevania style of gameplay?  

Is it going to be a RPG leveling system, is the player going to spend points to unlock the abilities, or maybe find them in game, a combination of the above?

The last thing is it going to require a high level of skill like dead cells/cuphead, or more casual based.  How are the characters going to be designed, pixel based, a clean look...

Just a thought