Let me count the ways:

- Uses huge amounts of memory
- Requires a fairly fast computer to run decently, even by today's standards
- Doesn't work well without using the Oracle JDK
- Basically huge and bloated
- Eclipse seems to excel at making you unproductive

Eclipse is most popular for Java, and Java projects have a way of becoming huge and bloated even when they aren't actually doing that much real work. When they get to this point, they need something equally horrible to manage them, such as Eclipse. The two go hand-in-hand.

I think most people just accept it because they haven't been exposed to anything better and it is at least free (oh joy!). Eclipse is the only IDE I know which has a website dedicated to hating on it : The Ultimate Place to Show Your Anger

Eclipse is the poster-child for what happens when you try to build a complex desktop application that runs completely on the JVM.