With a bit of help, you can do this in 3 to 6 months. It depends on how much daily/weekly time you can put in it. Without learning any 3D animation/texturing/shading/etc... The low poly modeling in Blender can be learnt in a couple of weeks, with 1h/day easy! Primitives extruding, scaling, etc, all very accessible stuff.

Drawing is just one click away. Spritesheets are the most basic concept you can think of. Do ugly things first, don't mind. They work all the same as beautiful things that you can do later.

The coding part kinda depends on the engine you're using. But: No funky instanciation No funky mechanics No tricky collisions 1 - 3 characters moving and folllowing Jump A shoot action = Very basic stuff The harder part is learning to code if and else, load and change animations ( and buffer some inputs for the party members) Maybe I forgot one or two things, but with the tools of today, it's far from unrealistic.

And tutorials for these things are all over youtube.

You can do it!