I think "not doing it" is a perfectly valid alternative
When people reject something as we are saying, “Let’s do all kinds of things,” it is tempting to say, “If you reject it, give an alternative.”
どんな立場の人でも「否定」するなら「代案」を出せ _打ち合わせはあまりにも身近で、そこかしこの企業で行われてきました。日本を代表するアートディレクター・クリエイティブディレクターである佐藤可士和氏も、その多忙な生活の多くを打ち合わせで費やしています。そして、たくさんの打ち合わせの経験から…_diamond.jp
However, I think “not doing something” is also a perfectly valid alternative. Deciding to do something means investing people and time, and more than anything, stopping something after it has been decided is often harder than not doing it in the first place.
So things that do not need to be done now should not be done.
That said, the important thing is that it be a positive decision. It is important not to list reasons why it cannot be done, but to judge the merits and then decide not to do it. In other words, as an alternative, I think it is good to say something like, “We should not do that now. Let’s move this other thing forward first.”
On the other hand, when brainstorming ideas, you must not reject them. If you read this article by Kashiwa Sato carefully, it is also about the time when ideas are being generated. When you are putting out many ideas, you must not step on the brake. It is also important to separate idea generation from idea review clearly, and I want not to forget that. It might be good to create a rule that forces narrowing things down.