You've structured this statement in a way that makes it unfalsifiable: if culture is organic and thriving, it's because capitalism hasn't touched it; yet if capitalism has touched it, then it must be inorganic and inauthentic. You're doing a "No True Scotsman" on culture as a whole, defining real culture as something that excludes any evidence capitalism could've produced it.

There are plenty of counterexamples for culture within capitalist society (forgetting for a moment that it's bizarre to conclude that capitalist culture doesn't count as culture if market forces touch it): hobbyist communities, open-source software, Wikipedia, fan fiction, folk traditions, religious practice, academic subcultures, internet memes, the entire DIY/punk schtick, local theater, oral traditions. All of those are orthogonal to market forces.

I think there are many things people mean by "capitalism". I think a system where people buy and trade stuff, getting income from their job is basically fine and almost a given.

Some people mean "capitalism" to mean: a state should be minimal, everybody should be doing everything in their power to seek profits and become maximally rich, becoming rich is simultaneously the utmost absolute charity you could do, and also the utmost personal happiness such that you shouldn't lift a finger for anyone else (of course, unless to particularly impacts yourself). That's the corrosive part I think. I think hypercapitalism (or money is my God) might be a better name for this, or some other term.

There are a number of associated malaises: along with believing money is the ultimate measure or virtue, come the belief that poor people are worthless (or worth much less), that being "productive" (generating profit or income) is the most important thing in life, that consumption of goods and services (i.e. things you buy with money) give you ultimate happiness (you just have to pick the 'right things' to buy), that any technological development is always perfectly good and can do no harm because it increases productivity, and that civil participation is unnecessary because the market sorts everything out. To name a few.