That might be true, or something local. I posted that this morning then got too busy to check in. I probably should have made it less about “positive/negative” and more about “it’s cool vs not cool” Here is my way too late OP explanation:
I go to a lot of sports events, hockey mostly. Since the 90s my friends and I play a little game. Count the people who give a #1 finger on the jumbotron vs point at their jersey vs thumbs up. Collectively, we have decided that ”kids today” don’t use thumbs up as much as in the past. I also noticed “Let’s go!” Is the cheer these days.
All good. I made a similar extrapolation the other day about pudding not seeming as popular because I wasn't seeing people eating it or it advertised but after voicing my thoughts to a coworker I realized I'm probably just not anywhere near the target market. I'm not a sugar crazed child watching children's TV networks and nor do I have kids myself.
OP, where do you live? I get thumbs up all the time. Sometimes as a greeting, sometimes as an encouragement (e.g. during a run), sometimes even as a means of communication in traffic.
I give thumbs up all the time. Usually two of them at the same time with a forced smile to let people know I wanna turn into oncoming traffic every day.
I used it three times this morning at the dentist because I couldn't talk. Also use it regularly at work to convey agreement. See others use it fairly often too.
*I love using thumbs up in a way that invokes absurdist situational irony by laying out an absurd situation that the other person expects an explanation for, but instead receives a friendly affirmation in the form of the thumbs up emoji, which exemplifies situational irony by subverting the other person's expectations of what the situation is actually about.
I use a thumbs up reaction as "I acknowledge I've read and understood this, but don't think you require a push notification" so I guess your mileage may vary