:-) or 😀 or U+1F600 does not unfortunately represent happiness in all cases. Sometimes i wonder when i last saw it representing genuine good.
Sometimes it’s an outright slap, when correcting someone who said something wrong*
Sometimes it’s a substitute for (😈, U+1F608), but cannot do so out of civility.
Sometimes you would discover that the person is in fact somewhat toxic. And uses :-) to encourage going in a direction, going for a call to action. It’s a bait in summary.
Sometimes the person is in a sad mood but sends :-) anyways.
Maybe it’s better not to use it at all.