And no taxes are not theft, they are a contract in exchange for citizenship and sovereignty of the nation. Evading taxes is theft, by you from the government.
You keep ignoring important parts of what's commonly considered the defining properties of the capitalist class, to make the idea seem less useful and much more slippery than it is. Or maybe taking that one sentence from WP as the entirety of the definition, period (though, again, ignoring important parts of that, even). I'm not sure you're going to find what you need to understand the concept, if you're interested, in an HN discussion.
If anyone can join then it's not exclusive. In fact it's entirely welcoming. The economy not only supports it but relies on it, demands it even, and the very people you may claim are the most powerful today includes members who have started with nothing and were far outside that 'class'. The boundary is completely porous and ever-shifting so as to be non-existent outside of a political discussion. There are no chains binding you.
So what is the use of such a definition other than a "us-vs-them" distraction? When the "them" is open to anyone? It seems like the side which is dividing and conquering is not the capitalists.
OK. I wrote a really long response attempting to get through, but frankly, at this point, you should write a paper and submit to some journals, because this whole line of reasoning would be a significant finding if it stands up to scrutiny.
Brevity is a key signal of clarity and cohesiveness. If it takes a journal paper to even attempt a discussion then this entire concept (under your interpretation) is suspect.
They're not muddying the definition. You're ignoring part of the definition.
Everyone has been consistent about what the definition is, and you have consistently pretended that part of the definition isn't there.
Are you calling it "muddy", then, because socioeconomic mobility exists? America's socioeconomic mobility is among the lowest of developed nations and getting worse since the 80s, but regardless, in order to even study such a thing requires defining it. Its definition is not muddy, it's widely accepted and studied.
I am genuinely happy for you that you were able to achieve it. I am incredibly grateful my parents were able to achieve it. But such achievements don't mean it's not still a problem.