While I do understand that private businesses are inherently exploitative and as a communist I seek to abolish such structures in favor of communal structures, am I wrong or misled to see companies like Valve Software as a major step up in comparison to others like Microsoft, Apple and the like?

Not entirely wrong. For sake of argument I won't address the actual shortcomings of Valve in practice as others already have here. I'll take it that for some reason Valve is actually a great company, Gabe is some great man with a progressive vision, etc, etc for the sake of argument.

There have always been within capitalism elements, even capitalists who have done progressive things or gone against the worst impulses of capitalism in their time for various reasons including genuine personal belief and conviction as well as marketing and carving out a niche. The problem is such sentiment is never widespread, often has some sort of contradiction or caveat to it (something bad they do despite overall being so much better than anyone around them by contrast), and rarely lasts much beyond the lifetime and/or control of the particular people pushing it (Gabe and others at Valve who work there but have significant control of what they and the company do).

So to be even a liberal capitalist who thinks that the Gabe/Valve way is the way to some form of ethical capitalism is to ignore history. It is to wishfully say well we just need more ethical, progressive people leading companies when the system itself disincentivizes this at any scale and indeed when it is as hardened and calcified as capitalism with as many old money types who have so much capital and so much push in the system of capitalism that while you can stand out of their way and do your thing up to a certain size you can't push them around, dislodge them, or dislodge how they're engineering the overall structure and you remain a fluke.

Capitalism is the way it is for a reason. It inevitably moves in this given direction and you can't stop it. It is its nature.

You mention China. China is different because they control the larger apparatus, they have a dictatorship over the capitalists and can use coercion and violence against them (and understand violence here doesn't just mean beating them with a truncheon it also means the violence of the state, they can harass them legally, intimidate them, make their lives uncomfortable and unpleasant in ways that involve no physical blows) if they step too far out of line and the capitalists know and are constrained by this though some still push (Jack Ma) and have to be checked and put back in their place.