You are wrong. Plenty of people write full length posts here along with posting pictures and other media. Some define it as “micro blogging” but it’s much more than that. Granted there are not as many bells and whistles as Blogger or WordPress but when you care mostly about content and getting your point across quickly this is a great platform for that. You also have a built in audience of millions of users which is nice too. Keep on blogging Tumblr nation.