WordPress is much easier to self host but much worse if you try to use it as social media. Most people who use Mastodon will want some Twitter-like experience. I don't think WordPress articles are going to replace toots any time soon.
On the other hand, Tumblr is supposedly working on ActivityPub integration, and that could become a major Fediverse player with the ability to replace Mastodon.
On the other hand, Tumblr is supposedly working on ActivityPub integration, and that could become a major Fediverse player with the ability to replace Mastodon.