There are great standard CMSes that do everything technically better than Wordpress (not that it's harder to jump higher than a rock, but hey). That's not the hard part. Every developer should build a good CMS once.

The hard part is displacing Wordpress market share; building a community of bloggers, marketeers, agencies, web designers, and so on; creating a huge ecosystem of paid and free plugins, allowing plugin devs to commit to your marketplace and lock customers in.

Wordpress is awful. The only thing it's got going is its moat, but that's not an engineering problem, but a people problem instead.