How do you think 2D beat-em-ups would have evolved if character action games (like DMC, God of War and Ninja Gaiden) and 3D games in general didn't end up replacing 2D beat-em-ups?Personally, I feel like 2D beat-em-ups would have gone in a similar route of increased character complexity. You see this with games like Final Fight 3 (released in 1995) and Guardians: Denjin Makai 2 (released in 1996) vastly improving upon character complexity with things like lots of motion inputs and lots of meter management. We probably still would have gotten juggles and style meters anyway (especially since fighting games like Tekken 3 and Marvel vs Capcom already was getting them), but with 2D games instead of 3D games like Devil May Cry 1.
More branching paths and rpg elements like in the D&D games. Or maybe more open world style like River City Ransom.
Probably the same way that non-retro 2D beat em ups evolved anyway, the genre only really took a break when 3D was the new hotness, but its always been building off of the Guardian Heroes style of making combat focus on juggles and other fighting game aspects, while a lot of them carry over Kunio aspects.