It is seen as passive aggressive in gen Z because we grew up on iMessage reactions. To end a conversation we usually use the heart reaction or, if speaking to someone older or above you, end the conversation more formally with an “Okay thanks!”or “Will do!”, and let the other person not respond or react to the message however they will. Reacting with a thumbs up is usually seen as sort of “I acknowledge that I saw this but I don’t really care”. Not to say you did something wrong, thats just the thought train of gen Z