I don't agree. I see no difference between using the laugh emoji to inappropriately laugh at someone's post and typing "LOL" to laugh at all of them at once. In either case, it's unkind.
I'm not a complainer - in fact, I subscribe to the idea that life is 10% what happens to you and 90% how you react to it. DH and I went to WDW a few weeks ago to use expiring DVC points and made the best of the limited experiences available. The heat and humidity were near record levels for that time in May and the masks outdoors were extremely uncomfortable. We dealt with it the best we could but there's no question it wasn't what we had originally planned (a family vacation for 7, which would have been our grandson's first WDW vacation). We had a good time, but I think it's okay to admit that there was also some disappointment.
WDW is near and dear to our hearts (no matter what you read here), and I think people are afraid it will never get back to pre-pandemic levels. That fear may cause a bit more lashing out at the current experience than usual. I suspect that some of the people laughing at the complaints have not been to WDW since the pandemic, so they may not fully comprehend the differences. Yes, some of the complaints seem over the top, but what's the point of making fun of them?