Only care about those people who are willing to listen to you even if that's your relative, at one point, you can't control your uncle's actions or decisions, and he has the right to make his own decisions. But it sounds good as a relative if shows him to be supportive and offers guidance and you could explain to him how meme coins and pink sale projects are often very high-risk investments and that there's no guarantee that they will succeed.
It seems your uncle wants to gamble his money, but if he can afford to pay with it, there's no problem with that at least, he might learn from a costly mistake like this and we hope they will get a profit on that project before it will collapse.
IMO, guiding him is the best solution if he is willing to listen to you.