Holding one up in a changing room, the question I always ask myself is what it's actually going to do for me, because tops are the thing we buy most and wear least thoughtfully. A shirt bought for one wedding ends up as the thing you grab for work, for weekends, for the school run. If it can't do at least two of those jobs without you fussing, put it back.
Fit is where most of these go wrong, and it's rarely about size so much as proportion. A top that's fine standing still can pull across the back the second you reach for something, or gape at the button if you've gone up a size for the shoulders. Check the armhole before anything else, that's the bit you can't fix later, and sit down in it if you can, because plenty of blouses look composed standing up and ride up the second you bend. Sleeves matter more than people admit too. Long sleeves that end an inch short look like a mistake, not a style choice, and I've learned to check that before I even think about the body of the thing.
The difference between a top that lasts and one that's bin-bound by October is almost always in the fabric and the seams, not the price tag. Cheap jersey goes thin and see through across the chest within a few washes, and you'll know a badly cut tee by how it twists at the side seam so the print or stripe ends up facing slightly the wrong way. Look at the inside, not just the outside, before you buy. French seams or a decent overlock finish tell you someone thought about the bit nobody sees. Buttons that feel light and plasticky will crack their shine in a month, and mesh or lace pieces live or die on whether the lining sits properly underneath, because a cheap lining shows every bit of underwear you own.
What a top clashes with is usually another loud thing at the same time, a heavily patterned skirt under a lace top, say, or a mesh piece worn over something with its own busy print, and suddenly you're wearing two outfits that are fighting rather than one that's finished. White tops are brutal in high summer heat and sweat, lovely in spring and autumn layered under something. Fine knits and anything delicate struggle in a heatwave commute, full stop, no clever washing fixes that. Cold hand washes and turning things inside out before a machine wash will keep colour and shape for a long time, tumble driers are where most tops quietly die.
No top will fix a bad fit on the bottom half, or make a rushed morning look considered. That's just not its job.