Hebrews 5:12 says the readers still needed what, instead of solid food?

Answer: Milk

Though they ought to be teachers, they needed milk, not solid food; whoever lives on milk is still an infant.

“Although by this time you ought to be teachers, you need someone to reteach you the basic principles of God’s word. You need milk, not solid food! For everyone who lives on milk is still an infant, inexperienced in the message of righteousness.”— Hebrews 5:12-13 (BSB)