It's not brainstorming though, it's just dismissiveness of a kind. It's trying to put forward this narrative that it's an easy problem, and it's not. If folks are serious about coming up with a solution to the problem, that's great, but it's unlikely to result from someone with no expertise in the field spending 30 seconds thinking about it and then moving on.

Which is what a lot of the pushback against those solutions illustrates, is the lack of depth of thinking about the problem that folks who "found a solution" exhibit. There are helpful suggestions and then there are half-assed unhelpful suggestions, and almost universally the "ideas" put forward by randos are the latter. Which is unfortunate, because there is value to collaboration and wide open problem solving, but this is not that.

Even more than that it's easy to see the root of these comments as fundamentally unhelpful. The starting assumption is that people are being stupid (across three separate national/international space programs) are missing something obvious, which comes about from this bias toward personal superiority and intelligence. Someone who was actually heavily invested in trying to help find a solution to the problem would start off by asking questions not proposing solutions. They would ask what the constraints are, what the full details of the problem are, what solutions have been investigated and found unsuitable, and so on. Instead you get people who just ride high on all of their assumptions and ignorance and don't even have the self-awareness to realize that's a problem. Is it smart to assume that Martian dust and Earth dust is identical with identical properties? Probably not, but it's a very common assumption by the solution havers. It's really easy to pretend that lazy, unhelpful advice is being made in good faith but it's generally not, and it's not being made with any level of thoughtfulness or effort behind it.

A good little comparison point here comes from the movie Pulp Fiction. In one scene a character, "The Wolf", is brought in to solve a problem, and the first thing they do is ask a bunch of questions to identify the scope and details of the situation, and then they proceed from there. That's just standard practice for any situation, even if you are a subject matter expert. You need to learn first then you can try proposing solutions. And if you aren't a subject matter expert (in, say, the design and operation of interplanetary spacecraft) then you should probably spend some time learning some details there as well. With that in mind, ask yourself what it would look like if someone really, truly was trying to be helpful in solving this problem, and if they put more than a few seconds of half-assed work into it, and then ask yourself how often you see comments of that nature that are actually thoughtful, informed, and potentially helpful.