For years I thought a blouse was just a shirt that had been to a nicer school. Bought a few in slippery polyester, hated how they clung to everything underneath and crept out of my waistband by eleven in the morning, and wrote the whole category off. It took a proper cotton one, with a bit of structure through the shoulder, to show me the issue was never the blouse. It was me buying the wrong weight of fabric for a body that moves around a lot during the day.
In the shop, or scrolling, the things actually worth checking are quite boring and nobody tells you them. Look at where the buttons sit across the chest, because that's where gaping happens, not at the neckline like you'd expect. If there's strain between two buttons on the hanger, there'll be a gap on you, and no amount of camisole underneath fixes that properly, it just disguises it until you lean forward. Check the sleeve too, specifically where it meets the shoulder, because a lot of cheaper blouses cut this too narrow and you'll feel it the first time you reach for something on a top shelf. And the back length matters more than people think. Too short and it rides up out of trousers the second you sit down, too long and it bunches oddly when tucked, like you've got a small pillow stashed at the back.
On the clashing front, a busy print blouse with a busy anything else is a lot, visually, and I say this as someone who once wore a floral blouse under a plaid coat and looked like a sofa that had given up. Heavy jewellery around the neck fights the collar for attention too, particularly on anything with a tie neck or a frill, you end up choosing one focal point or the other, not both. And thick belts over a soft, draping blouse tend to just crush the nice movement of the fabric into something stiff.
Where it genuinely isn't the right choice: anything physical. A blouse with a proper day of lifting, carrying, bending, it will show every crease and probably gape somewhere it shouldn't by lunchtime. Same with very hot weather if it's not a breathable fabric, because the cling returns and so does the regret. And if you need to move fast, catch a bus, run for a train, the delicate ones with covered buttons or fiddly cuffs will slow you down at exactly the wrong moment.
Get the fit right through the chest and shoulder, in a fabric that actually breathes, and it quietly does more for a plain pair of trousers than most things in the wash pile.