I'm pretty confused about it. The reason I've seen for them not liking it doesn't make sense. As far as I can tell you, they view it as the person investing doesn't provide any value. Which isn't true. The person investing provides a resource for the people to use. How I view investing is like how a farmer will give a chef food to cook with. The farmer has a resource, and the chef needs the resource, so the farmer and chef trade. Farmer gets money, and chef gets a resource. The farmer got a little bit more back than he put in. The chef will cook a meal and make a profit as well. None of that is viewed as exploitative as far as I understand. Well, investing is just that, except you leave the resource and all the profit you make with that resource to the person you invested in. Eventually, you'll pull the money you put in plus what every profits you have over time. Which is like if the farmer gave the resource to the chef and told the chef to pay him back later. So I'm not sure if both of those are exploitative or if there is some difference I'm missing. I've only just started researching into socialism, so sorry if this is common knowledge.

Edit: I do understand it CAN be exploitative. I just don't understand why it's viewed as inherently exploitative.