Indeed, and the fact that around 60% of the population is living on subsistence wages underscores the point. They literally pay people just enough for them to keep working, literally all the value produced through labor is appropriated by the parasites.

I would definitely call it theft in most cases, because in a capitalist system, labor is structurally coerced and is not giving up its surplus value freely, as you basically said yourself in different words. Or perhaps more succinctly, I would call slavery a form of theft. But I agree it isn't "wage theft" because that has a more specific understood meaning related to what's owed according to the law.

also wage theft is a specific thing: failing to pay wages or benefits owed in a contract… things like not paying overtime, etc

conflating terms makes it difficult for people to educate themselves and know what their actual legal rights and options are

Workers have right; those right are poorly applied but workers have unions to defend themselves. Slaves have none. This is a big difference, and being exploited is enough to be outraged; we do need to make confusion that would invisible people enslaved

The name of the game is exploit or be exploited. Either you're a capitalist or a worker.