In case you haven't realised, it's a wedge issue.
If you really care about refugees, wouldn't you want them to avoid endangering their lives by getting to Indonesia (probably a dangerous journey in itself), raising thousands of dollars (how do you make $5,000 in Indonesia? I'm guessing they have to do a few things which they really would rather not do), and then putting their lives in the hands of people smugglers (probably not for the first time).
They aren't coming directly. There are easier ways to get to a UN refugee camp.
It's a complex issue, if you care about refugees, and both sides have merits. On the other hand, if you don't care about refugees, the answer is pretty simple. So it's a wedge issue.
The left is split between the people who want to accept asylum seekers, and the people who think it's better to encourage them to go through the offshore process.
And you should note, Australia permanently resettles about 6 refugees per 100,000. Only Canada and NZ does better. The US resettles about 4. There's a few other countries which aren't totally shit, but most of the world is really really terrible about resettling refugees. Australia is one of the few countries which actually pulls its weight here.