Keeping the tone casual and at their level should work better. If it sounds like an exam question or job interview, kids would find it difficult to engage. It's a learning process for adults, too.
Thinking about our own childhood and how we would react to the critical thinking questions should help. Instead of a pop quiz sounding questions, we would prefer the adults talking to us to be genuine and not trying to lecture us, or test us.
You wouldn't talk to your friend in a way "what's the streamer's motivations?" but you'd make a conversation out of it. "I was there with them right until they said this..." And you'd state your reasoning. Think of it talking to your friend, but keep it 12 yo. level.
Sorry for adding comment after comment, I've been in a position to talk to teenagers and experienced when they tune you out, when they're interested in what you have to say.
I find it works best if you start with the positive. As adults, we should challenge ourselves to find the positive at times, since we tend to slide into correction mode without realizing.
Sometimes, we'll start with positive and then talk about the part that's problematic and why. Sometimes, we should just mention the positives, good examples, well thought out arguments, a good word choice etc. In fact, noticing and mentioning good examples will be the real game changers.
And be genuine, I cannot state the importance of this at all. Consider what your friend would think of the tone you're about to use. If your friends would think you're trying to preach, your kid will feel the same.