Why it is useless?
Either because of bugs (kill/damage tracking, emplacements not appearing, efficiency been bugged, etc.) or due to how you need to understand the context behind the game you played in order to extrapolate any useful information. At which point, you might as well just watch the replay.
To give some specific examples of why the stat screen is useless:
Army Value is based on raw numbers, not the actual strength of units (particularly not in specific contexts). Unit "value" isnt a valuable statistic.
Kills/deaths are exceedingly misleading due to several bugs: examples of which include: A: USF crewed tanks count as five "deaths/kills" each, due to their associated vehicle crews. B: An S-Mine that detonates counts as a "death" for the Ostheer player for some reason. Other mines don't have this issue. There are other similar issues, but I dont think there's a need to provide an exhaustive list.
Damage is misleading because you can't translate it to any sort of useful metric. Infantry have 80 hitpoints, but doing 80 damage (Or any multiple of 80) to infantry doesn't mean you've killed x numbers of infantry, as they may simply be wounded and subsequently heal. The damage numbers aren't even divided between infantry and vehicles, and the latter have the lion's share of HP. The only thing you can really glean from high "damage" is that a player has damaged a lot of vehicles... but not that he's necessarily even killed any of them.
The only vaguely useful statistics might be Manpower/Munitions/Fuel spent, and how much of any of those you have taken away from the enemy through model drops and vehicle deaths. These stats arent displayed, though.