Wordpress & Google's Blogger both have Apps for this. I don't know how much more simple one can get than these? My webhost never could get wordpress installed on my site, so I've been playing with Blogger & it's very easy to me. The biggest slowdown I find is via the phone, resizing the 8 MP images down & making edits before posting them. Or for images that are not of great concern, I set the camera adjustments for image capture to be smaller resolution & have greater sharpening meant for a blog post.
I'm not familiar with other apps & don't participate in social media sites like Farcebook, Fl*cker, & so on.