The plugin ecosystem is full of freemium garbage. It's also designed so a functional site basically requires the jetpack plugin, which is a connector to automattic's proprietary SaaS.
The codebase is old, like mostly procedural PHP. It's got a long history of security issues, and is just a pain to work with. And it's run by a megalomaniac who doesn't seem to understand what running an open source project is about.
I could open-source defecating into your hands and clapping if you like, but it probably won’t increase demand or convert people, even open source advocates, into true believers if they don’t already like doing it.
And there are absolutely problems with Mullenweg’s stewardship, whatever else you might think of the product.