For just regular text to be consumed by humans, it's not that great, you probably want a word processor.

It shines when you do a lot of more structural editing, stuff like "change all quotation marks on this line to be single tick", "copy everything inside these parentheses and paste it after the equals sign", "make the first word on the next five lines uppercase", these are the type of things vim make easy that are not easy in other editors.

So it's great for code and config files. Markdown is borderline. You can have a setup that lets you live view how the markdown renders while editing in vim, so it can be pretty good, but the advantage might be a bit dubious.