For a small investor like me, a junk bond ETF with a well diversified portfolio is a way to invest in junk bonds.

Let's face it.  junk bonds are not investment grade--meaning there is a higher risk of default in the event of adverse events.  I could lose my shirt, um, entire investment if I buy the junk of a single issuer.  The junk of a single issuer being all I could afford when buying individual bonds.

By owning a piece of a well diversified pool, I am protected by diversification in the event a few issues in the pool go bad.