Socialism is a lot more than just 'who owns the means of production', that's just a very crude paraphrase of Marxism, almost just a slogan. Socialism proper is much more broad, including anything that encourages consideration for your fellow man as opposed to selfish individualism, like institutions built for their general welfare that serve society at large. Such notions predate communism by a considerable margin, with examples being the St Simonians and the Fourierists.

There can be no middle ground between the two, it's by definition mutually exclusive

What and whose definitions? This seems more than a little ignorantly dogmatic and a bit overzealous, since many businesses are owned (that is to say a claim is made on a portion of their capital, i.e. their 'means of production') by a mixture of private and public interests, a basic feature of so called mixed economies (the vast majority, if not all). Be careful of false dichotomies, that deny any space, considerable distance, or any possibilities between opposing camps and their positions. This isn't claiming they're perfect systems that can't be significantly improved, nor that capitalists and communists aren't diametrically opposed ideologically, only noting that for some there are shades of gray between those polar positions, latitudes if you will, that other related groups may inhabit. If you can imagine a gradual revolution, perhaps like Lenin, it may be necessary to inhabit and move through such regions to attain the desired final political end.