Just adding to the lists from the previous replies:
Bad:
Sealed Grand Celestial Steel - Remove, or severely drop the gold cost (24g to like, 50 Silver), or replace with large stack of GC Steel.
Warrior's Scale/Fragment Selection Chest - Outdated & too small an amount from the chests.
Dokkaebi Soju - Really old, replace with something better.
10,000 & 100,000 Exp Charms - Remove, add 5 million Charm and 10 million Exp Charms.
Sealed Scarlet Conservatory Weapon Materials (Frond, Oculus, Stalk) - Outdated. Remove / replace with More common Steelbreaker weapon materials. The story + a week of daily challenge can just about get a player to Thornbreaker 6.
Steelbreaker & Thornbreaker Soul Shield Chests - Make much more common and way less gold. 2+ tiers behind at this point.
Greater Naryu Sanctum Bracelet Chest / House of Idols / Thornwind Accessory Chests - Outdated, should be more common and cheaper.
Suggestions:
Higher quantities of the items in a 1-star roll earlier on e.g. 10 Imperial Soju instead of 1, 5 Resurrection Charms instead of 1, etc.
Bring in more past cosmetics/skins (maybe do polls to see what players want to see come back).