The mistake is treating white as one color, screwing in whatever bulb was cheapest that week, and then wondering why the porch looks like a parking garage while the string lights over the patio look like a hospital corridor. White outdoor light runs from a soft, almost buttery glow all the way to a blue tinged daylight white, and those two things do not read the same way once the sun goes down. You have to pick a temperature on purpose, not by accident.
Warmer white suits the rooms you actually sit in after dark, a back porch, a deck off the kitchen, string lights over a small patio table where you're having a glass of wine and not trying to perform surgery. It works year round but it earns its keep most in fall and winter, when everyone wants the outside to feel like an extension of the living room instead of a floodlit yard. Cooler, crisper white belongs somewhere with a job to do, a driveway, steps, a side path where you need to actually see what you're walking on, and it suits a more modern house, clean lines, lots of glass, where a warm glow would look like it wandered in from the wrong building.
Where it goes wrong is mixing temperatures on the same wall or the same run without meaning to, one warm bulb and one cool bulb on the same fixture looks like a mistake because it is one, and it's the kind of thing that bugs you every single night until you fix it. It also clashes with anything trying hard to look rustic, exposed brick, weathered wood, string lights with that very cool, very blue white look wrong there the way a fluorescent tube looks wrong in a cabin.
In an ordinary yard, white light sits easily with whatever you already have, dark bronze or black fixtures, a wood fence, string lights crossed over a plain concrete patio, a lantern by the front door. It doesn't need a matching theme, it just needs you to decide once what mood you're going for and stay consistent down the whole side of the house.
If you've got nothing out there yet, start with one warm white string light set for the patio or porch, it's the one that gets used the most and forgives the most, and it makes a plain backyard feel lived in within one evening instead of making you second guess the whole setup.