IDE's are terrible.
They are large, slow and bloated. They discourage experimentation. They don't work well over a remote connection.
It takes way too much mental effort to make a new program in an IDE. They generally want to create a directory and project files and who knows what else for you when all you want to do is write some fucking code.
The other problem is that there's no generic way for a programming language to provide support for multiple IDEs. It ends up being a nasty problem--programming languages and IDEs shouldn't be so closely tied to one another. Developers would be better served by bringing their own tools rather than learning a new IDE.
IDEs encourage the production of code that can only be maintained and understood with the help of a sufficiently powerful IDE.
Some people like them and use them non-destructively, and those people should be supported. Easy access to documentation, fast and accurate code navigation, and automatic refactoring are all good things.
I think it's better to build a non-integrated development environment from discrete components, and then let users bring their own editors, build systems, etc. If those happen to be existing IDEs, then so be it.