Many people in the industry have a very glorified view of FAANGs, and in particular one of the reasons that many people want to work at a FAANG is because of the idea of working and learning from the most impressive people in your field. If you've ever heard the saying "if you feel like you're the smartest person in the room, you're in the wrong room", I think that is a saying that these types of people ascribe to.
The problem is that oftentimes someone joins a FAANG and that glorified view is shattered. The reality is that the people at a FAANG are not necessarily geniuses (there are geniuses at FAANG, as there are at any company, but they are far and few between compared to the 'average' FAANG engineer). I work at a FAANG (look at my name and you can guess which one) and I would certainly say that it is very frustrating to me that my career has felt like it has effectively stalled ever since joining, because everyone on my team is just as clueless as I am and I do not find any of my direct or extended teammates particularly impressive or inspiring.
When this happens, the "shattering" reality that your new job isn't some wonderland and is full of all the same issues of your old companies can make you quite frustrated and dissapointed, and it's quite easy to place that blame on your coworkers or the tools they use. I don't think it's disdain as much as it is disappointment, and OP probably feels like they were sold a false bill of goods. I know I certainly relate to that a lot.