Starting point
For men
Where a wardrobe gets hard when convention allows fewer silhouettes and the difference between two greys is doing the work.
Not fewer clothes. A narrower band of what most workplaces and most events read as unremarkable. Skirts, dresses and heavy layering are wardrobe items like any other, and the app treats them that way. The constraint is social, not technical, and it is worth naming as social rather than pretending it is a fact about bodies.
The practical effect is that when convention allows fewer silhouettes, the difference between one outfit and another has to be carried by smaller things.

Where it actually gets hard
The margins are narrower. If a shirt, trousers and a jacket are most of what is expected, then fit, fabric and shade are doing all the work. Those are exactly the things that are hard to judge from a hanger and easy to get slightly wrong.
Colour, more often than anything else. Navy against black, two greys that turn out not to match, a brown belt with black shoes. These are hard to call from memory for anyone, and they get harder when most of the wardrobe sits in the same narrow range. Colour vision deficiency also runs about one in twelve among men against one in two hundred among women, for inherited reasons. Either way the fix is the same and it is not advice: put the two things next to each other and look.
Fit is most of it. A cheap garment that fits reads better than an expensive one that does not. Shoulder seams, sleeve length, where the trouser breaks. Hard to judge in a changing-room mirror at an angle, straightforward when you can see the whole body at once. Sizing between brands is no more consistent here than anywhere else.
Dress codes with no gradient. Smart casual is genuinely ambiguous, and both failure modes are live: a suit where nobody else wore one, or trainers where they were the only pair.
Occasion clothing bought under pressure. A wedding in three weeks, a suit bought in a hurry, worn once. Whether it still fits is unknown until the morning of the next one.
What the app does about it
What happens
You cannot tell whether the navy jacket works with the grey trousers, and asking feels ridiculous.
What DROBE does
Look at it on the avatar. You are choosing between two pictures, which is a much easier question than the one you were being asked.
What happens
Two black items that are different blacks, and the difference only shows in daylight.
What DROBE does
Both photographed under the same light, side by side in the grid. The mismatch is obvious before you leave.
What happens
The suit from the last wedding. Does it still fit? Unknown until the morning of the next one.
What DROBE does
The avatar reflects your body now, not the body you had when you bought it.
What happens
You would wear something less standard but cannot picture whether it works, and the shop mirror is not the place to find out.
What DROBE does
It is an item in the wardrobe like any other. Put it on the avatar and look, with nobody watching.
What happens
Presenting at work and unsure whether the shirt is too much, too little, or wrong on camera.
What DROBE does
See speaking on a stage. Stripes, pure white and where a microphone clips are technical facts, not opinions.

Start with an ordinary Tuesday, or with a second opinion on what goes together.