SharePoint vs the Rest
Wordpress is a blogging platform and SharePoint has a blogging template site. Both offer out-of-the-box capabilities to setup a blog without any programming knowledge but differ significantly in the underlying technology and process.
Sitecore is an enterprise cms known for it's digital maketing features and sharePoint has a publishing feature that offers cms type capabilities for internet, extranet and intranet sites. Sitecore is available through a paid license and is on the more expensive side of cms'. The publishing feature in SharePoint is included in the enterprise server version which is now the only version of SharePoint available. You can still host sites using the SharePoint publishing feature but the ability of hosting a public facing site is no longer available through Office 365, SharePoint online.
Confluence and SharePoint are both collaboration platforms. Confluence is part of the Atlassian workplace productivity suite of products and SharePoint is part of Microsoft's suite of Office products. They both have an on-premise version but more and more organizations are moving to their cloud-based versions.