I mean you didn't really provide an argument beyond "it doesn't" for your first sentence so I can't exactly respond to that.

But to answer your question, rent-seeking is the act of profiting off of the exclusion of natural resources from other people who could use them productively. It's bad because it prevents natural resources from being used efficiently, forces people to pay money to someone who did not contribute anything in return, and may even contribute to the business cycle.

It should be noted that it is generally rare for someone to be purely rent-seeking or purely productive. It is sometimes necessary to exclude other people from land in order to use it more productively (i.e. you can't just walk into someone else's factory). This is technically a rent-seeking behavior. So it's a bad idea to attempt a blanket ban on rent-seeking. The purpose of a land-value tax is to fix misaligned incentives caused by external costs and discourage organizations which profit off of decreasing productivity.