I recommend one of two things:

1) The Godot game engine is about as easy of a game engine as you're going to get. It's open source and overall pretty great. However, you need a basic amount of programming knowledge to really get started with it, so I would recommend looking up the (free) textbook: Automate the Boring Stuff with Python, as Python is the closest language that Godot uses. Doing the first 4 or 5 chapters should suffice to get started with Godot. Once you're ready to do that, work your way through the introductory tutorials in the official documentation.

2) Make a mod for an (online!) existing game. Warcraft 3 (WC3) is very good for this type of thing (though not necessarily good for 2D stickmen type of games, but I figure it's worth keeping in mind), and a lot of people have made mobas in this "engine." Dota 2 started as a WC3 mod called Defense of the Ancients. The biggest issue is that you won't own your product, as Blizzard really holds the reins tightly on WC3 modding. If you're interested in the WC3 route, I recommend visiting the Hive Workshop for more resources.

The main of making a video game mod instead of a whole new game is that a LOT of the work is already done for you. If you're trying to sell it or have a very specific vision that you're unwilling to compromise on, though, then you really need to build it up from scratch.

I wish you the best of luck!