I assume you are new, so I suggest you use Unity3D. Never worked with Unity, but I know that a lot has already been implemented for you. For example: animation, gravity and collision. Class comrades told me that it is not so difficult (for a student programmer). They used it for an AI project.
I took the XNA lesson, and XNA and monogame are pretty much the same. Monogame is a low-level platform. You must implement all this yourself. I would not call it an engine, but rather a frame.
Since XNA is dead, I asked my teacher: "Why do we learn XHA if XNA is dead?" Well, we didn't recognize xna because XNA is so awesome, but because it's low. If you know how to do this with XNA, you can probably work with any other low-level conditions. Especially since I would use Unity if I were you.
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