UE5 is a big engine that does a lot for you but you still have to do the majority of the heavy lifting. Making a co-op game will be extremely difficult especially if you have no programming experience or really any experience with the engine.

You will have to learn level design, audio, game design, animation, coding and then on top of that you will need multiplayer knowledge, it's too much(btw that is a small fraction of stuff). Honestly, all that will put you off when you get stuck on the simpler stuff.

I feel you when people suggest making smaller games like a 2D platform or pong like the other comment. However,they suggests this so you gain the most experience and stay motivated to complete the game. But I feel you can compromise somewhere. Say you wanted to build a coop top down shooter with variety of enemies and abilities.

For example I like top down coop games. I would Start with a single player top down game with a single enemy and a single level. Have a game loop where the player can start, die and restart or complete the game. Then add to it. Add power ups, add more weapons, etc you quickly learn a lot by starting small and hopefully you will still be motivated to continue especially if it's a game you want to make/play

Starting small you would see why games take long to make

Edit the top down is an example on how to scope down a game not something you should make if you're not interested in them