It's a question of scale, and balance. Yes, I think it is ridiculous to ask for donations to keep unwanted dogs alive when there are people on the same island who are suffering.
There are many bad things happening everywhere. That doesn't mean we shouldn't try and stack-rank them, in order to allocate funds effectively. There's diminishing returns to everything[0]. As you throw money at problem #1, it becomes more and more expensive to make a marginal improvement, so eventually, it swaps places with some other problem in the ranking.
There are many criteria you could use for making such ranking of problems (a popular one is minimizing dollars per lives saved, or dollars per QALY added). Living in a free society means people are free to decide how much (if anything all) they want to spend on charitable causes, and on which ones. But in one's individual spending, it's worth to think about how to get maximum "bang for your buck", in terms of alleviating suffering.