It is true that one person's spending is another person's income but that doesn't capture the waste. While wealth isn't a zero sum game, the time of the population as a whole and the low entropy (resources) of this planet is. If you employ someone to pilot your private jet, that person isn't able to do more productive things such as pilot a plane with more people on it. In capitalism, your wallet is like a vote: you get to influence how other people spend their time and how resources are allocated.
> Why judge what people buy with their own money? Isn't hard enough to judge what you buy with your own money?
I'll give the benefit of the doubt for most things. I'm sure people will judge some of my consumption as wasteful. I do think there is a threshold in which we can tell the consumer, "I think you can do better": imagine if you hired a person to burn trees all day - and I'm not talking about slash and burn agriculture or generating power using the resulting steam/heat - just literally burning trees. I'm open to be convinced that private jets are within the threshold but as of now I don't agree.