The fallacy of appeal to worse problems (or relative privation) occurs when someone argues that efforts spent to solve a specific problem are a waste by pointing out that there are bigger problems that need to be solved.
Space research is a common target of appeal to worse problems. Flat-Earthers use it to discredit space research and to make people emotional. In reality, it is possible to care about multiple problems simultaneously, and solving the supposed smaller problems does not mean the bigger one is considered unimportant.
Some results of space research appear impressive and give the appearance that they are overly expensive. However, usually, space research is not as expensive as it might look. For example, the Perseverance mission to Mars only cost about 0.0075% out of the total US government budget from 2013 to 2020. This is minuscule compared to the proportion of the budget allocated to social security and defense. And it does not mean the expense just vanished, but the spending goes to the economy, providing people with jobs.
Not many people have sufficient information about the proportion of the budget allocated to research. Unscrupulous conspiracy theorists exploit the fact —flat-Earthers included— to make people emotional. They would compare the nominal amount of the budget with something like humanitarian efforts.
By such a “logic,” we can dismiss pretty much all efforts to solve anything as a “waste” as long as we can find something, anything that can be regarded as “more important.”