I think a lot of people object to the labour practices of most if not all of the food delivery services; this isn't particularly new news. In Australia the drivers/riders are not treated or paid very well and there is considerable controversy about whether they are really employees vs contractors.
I'm surprised that this hasn't occurred to you already at least as an issue for someone (not necessarily you, or, for that matter, me). Still, this given that this is a thread where things like "food delivery" need to be explained from first principles, I shouldn't be too surprised.
> In Australia the drivers/riders are not treated or paid very well
So they should do something else. Those drivers determined that delivering the food was the best use of their time. I don't think it's right to voluntarily choose this specific job and then make people feel immoral for using the service they signed up to provide.
Well, some of the ways they are not treated well seem to be sailing pretty close to the wind in terms of Australian labour law or are outright illegal. It's also pretty hard to imagine these services being remotely workable without a steady supply of "students" who are in Australia supposedly earning degrees but in practice are a giant pool of cheap labour. You can make various libertarian quibbles about both Australian labour and immigration rules, but not everyone wishes to subscribe to your libertarian newsletter....
What does having a conscience have to do with whether or not you use a food delivery service?