Howard Marks is not going to get invited to this weekend’s Ethereum anniversary party, that’s for sure.

Mr. Marks, the billionaire investor and co-founder of Oaktree Capital Management, takes a scythe to digital currencies in his latest investment letter. To be fair, he swings the same scythe across basically the entire investment landscape, seeing warped valuations everywhere and nothing but lousy returns to come. Uncertainties abound, from economic growth to central-bank impacts, inflation and political dysfunction, yet investors are still embracing risk and pushing up prices. “In general, the best we can do is look for things that are less over-priced than others.”

Mr. Marks is a long-time Wall Street denizen who founded Oaktree in 1995 and made his name investing in high-yield bonds and distressed debt – especially during the financial crisis, when he raised $11 billion to buy bonds (and cleaned up on the bet). He is also known for his well-written, plainspoken investment letters, which tend to cast a critical eye on the markets. No less than Warren Buffett urged Mr. Marks to collect some of his past writing into a book.