For years I stuck with the single flush ceiling light every rental bathroom seems to come with, the one that makes everyone look slightly ill, because I figured bathroom lighting wasn't worth thinking about in a room I didn't own. What changed my mind was standing at a mirror trying to put on makeup under a light so flat and yellow I couldn't tell what color anything actually was, and realizing I'd rather deal with an electrician than keep doing that.
The honest limit is that a lot of bathroom lights need real wiring, not a lamp you plug in, so if you're renting and can't touch the fixtures, you're mostly working with what's already there plus a mirror light or a plug in sconce if you're lucky enough to have an outlet near the mirror. And even if you own the place, this isn't a room for mood lighting alone. One soft, warm fixture over the tub might look lovely for about ten minutes until you're trying to see a splinter or check a rash on a kid at eleven at night and there's nothing bright enough in the room to actually see by. You want layers if you can get them, something dim and gentle for evenings and something closer to daylight near the mirror for the actual business of getting ready.
Where it goes wrong is matching it too hard to the rest of the house. A heavy, ornate fixture that looks right in a dining room can feel completely out of place over a small bathroom sink, especially in an older apartment where the ceilings are already low and busy with trim. It also clashes with cool toned tile if the light itself runs warm, you get this strange orange cast on blue or gray tile that no amount of candles fixes. I learned that one the hard way in a bathroom with pale gray subway tile and a fixture that turned everything the color of weak tea.
For finishes, I've had the best luck with simple opal or frosted glass, brushed nickel, and matte black, because they don't show water spots the way polished chrome does and they sit quietly against whatever tile or paint you've already got, white, gray, pale blue, almost anything. Warm white bulbs around 2700 to 3000 kelvin near the mirror are the easiest on everyone's face, no clinical blue, no murky yellow.
The detail that makes a good bathroom light worth having is a dimmer, even a cheap plug in one on a lamp style sconce, so three in the morning doesn't mean full interrogation lighting.