The first black skirt I owned came from a supermarket clothing rail, a stretchy jersey thing with a waistband that rolled down the second I sat for more than twenty minutes. It taught me that black fabric forgives almost every fit problem except that one, and that a skirt you have to keep tugging back into place is never going to earn a place in a proper rotation, no matter how cheap it was.
Black on black sounds foolproof and mostly is, but it has its own small ways of going wrong. Pair a matte skirt with tights that have even a slight sheen and you get two different blacks arguing with each other under any decent light, which nobody notices on you but everyone notices in photos. The same goes for mixing a cotton skirt with a skirt-shaped bag or shoe in a blue black rather than a true black, it reads as mismatched even when both items are perfectly nice on their own. A heavily textured or boxy jumper on top can also swamp the line of a fitted skirt, so the shape you worked for disappears under knit. In the shop, I always do the same few checks before anything goes in the basket: hold the fabric up to a window to see if it goes see through over the hips when it stretches, check whether the lining (if there is one) sits a sensible length below the hem rather than peeking out, and sit down in it right there if you can, because a skirt that rides up to mid thigh the second you sit is a skirt you will spend all day adjusting. Zips at the side rather than the back tend to lie flatter under a jumper, which matters more than it sounds like it should.
The honest limits are mostly about fabric and occasion rather than the colour itself. A cheap synthetic black skirt will often go slightly grey or take on a faint sheen after a handful of washes, especially if it's been through a hot cycle by mistake, and no amount of ironing brings true black back once the dye has given up. Elastic waistbands soften over a season of wear until the skirt sits lower than you bought it for. And for anything that needs real formality, a thin, slightly see through black skirt just won't carry the weight, you need something with proper structure or a lining built in, not a flimsy layer doing its best.
A well made one does get better with wear, oddly. The creases from being folded in a bag drop out on their own by the time you've worn it a few hours, and the fabric starts moving with you instead of against you.
So before I buy, I ask myself one thing: will this still look properly black, and still sit where I put it, after it's been washed a dozen times and stuffed in a bag at least once?