This is perhaps a bit cavalier, but I'm going to say it anyway. A blog needs either a personality or an editorial calendar.
People are interested in people, particularly in people whose interests are the same as theirs. If you find a blog in a field that interests you that is written by somebody with a distinctive voice and some interesting things to say, you will follow the and you will give them a lot of slack when their posting schedule is erratic and when they sometimes get a bit off topic.
If you have a personality and an interest that is shared by other people, then you are probably fine just to write what you want when you want.
If you are a corporation that is creating a blog as a content marketing tool, then, almost by definition, you don't have a personality or anything interesting to say and you have plan very carefully to give the reader the appearance that you do. In this case, you definitely need an editorial calendar.