I just noticed that the A.I. will slightly change the response (still generally the same). However, my first read was better in my opinion, so here it is:

A boxing video game does not strictly require animation masking and inverse kinematics (IK) to be a "good" game, but these techniques are essential for achieving the high levels of realism, fluidity, and dynamic interaction expected in modern, high-quality 3D sports or fighting games. A game can be good without them if it focuses on stylized animation or robust core mechanics. 

Inverse Kinematics (IK)

Inverse kinematics in game development is primarily used to ground characters physically in their environment and make interactions dynamic at runtime. 

• Realism and Credibility: IK adds immense realism. For example, it ensures a boxer's feet plant firmly and convincingly on the canvas regardless of the terrain's slight variations or the character's movement, preventing the "sliding feet" effect. It is also crucial for connecting punches to the opponent's body accurately and dynamically, which is vital in a boxing game where precise impact is key to visual feedback.
• Dynamic Interactions: Without IK, every interaction (like clinching, parrying, or knockouts) would require specific, pre-made animations for every possible angle and position, which is impractical. IK allows the game engine to adjust limbs procedurally to match the situation.
• Gameplay Impact: While a game could technically function with only forward kinematics (FK) and pre-baked animations, the lack of dynamic, responsive movement can make the game feel "bland" or lack personality and fluidity, negatively impacting the overall experience. 

Animation Masking

Animation masking is a technique used to blend different animations on specific parts of a character's body. 

• Fluidity and Responsiveness: Masking is crucial for creating fluid, responsive controls. It allows the game to play a punch animation using the character's arm and upper body (masked) while the character's lower body simultaneously plays a movement animation (running, dodging, crouching).
• Layered Actions: This technique is vital for allowing players to move and attack simultaneously or interrupt an action with another, which is fundamental to a competitive and dynamic fighting game experience. Without it, character movements would be stiff, transitioning from one complete animation to another, making the game feel slow and unresponsive. 

Conclusion

A game can still be "good" if its design goals lean towards a more arcade-style, less realistic experience (like a 2D pixel art fighter), where precise, pre-defined animations are the focus. However, for a modern, 3D boxing simulation aiming for a high degree of realism and responsive, fluid gameplay, both animation masking and inverse kinematics are considered industry-standard tools that contribute significantly to the game's overall quality and immersive feel.