I don't get what makes it hard to animate.
You make a slightly different animation if they are standing and get hit...projectiles they fall backwards forcibly onto the ground (like being pushed), normals they can drop like they do now, physical specials makes them hit the ground harder. If they are mid combo, once they hit the ground, they struggle to get up but fall back down and stay there. There also needs to be a more definitive sign that the opponent lost, like what happens when you hit Jason in unstoppable before he has the option to revive, where it's a bit of a firework-like animation (loosely translated) and slow motion for a second. Many FGs have that "Last Hit Animation", Tekken does the slow mo which looks awesome, SFV has the painful cry at the end, so-on.
I've hated the way matches ended since IGAU.