I see propitiation has been consigned to the $5.00 dust bin of history. What the word means is "the means of salvation." Those placed in the propitiatory shelter are saved, those not in Christ unsaved, facing God's wrath for their sins. In Romans 3:25 and Hebrews 9:5 we see the noun indicating Christ as the propitiatory shelter providing the means of salvation.
Romans 3:25
whom God displayed publicly as
the means of salvation by His blood through faith.
This was to demonstrate His righteousness, because in the forbearance of God He passed over the sins previously committed;
Hebrews 9:5
and above it
were the cherubim of glory overshadowing the
means of salvation but of these things we cannot now speak in detail.
In Hebrews 2:17 we see the verb indicating Christ as providing the means of salvation.
Hebrews 2:17
Therefore, He had to be made like His brethren in all things, so that He might become a merciful and faithful high priest in things pertaining to God, to
provide the means of salvation for the sins of the people.