This book of the Bible tells us
Jesus is superior to the Angels (Hebrews 1)
Jesus is superior to Moses (Hebrews 3)
Jesus is superior to the law (Hebrews 7:19)
Jesus offered a better testament than the old (Hebrews 7:22)
Jesus mediated “a better covenant, which was established upon better promises” (Hebrews 8:6)
Jesus offered a better sacrifice than that of the Levitical priesthood (Hebrews 10:11-12)
Jesus, a priest after the order of Melchisedec, is superior to the Levitical priesthood (Hebrews 7)
so it is appropriately named Hebrews.