gacha have element of chance, but usually speaking, gacha especially in asian games tend to also be tied to some form of power and is not purely cosmetic.

ao its not just purely, i want this character/costume/weapon because it looks cool, but theyres stats attached to it.

western game loot boxes generally sit more often as coametic, so the desire to pay isnt as bad (but can still be bad) but of course this doesnt apply to all western games either. an example of gacha based power is ultimate teams for sports games, which its gacha has players stats tied to them for team building.

gacha and loot boxes are fundamentally the same, but connotatively, gacha usually implies power and lootbox implies cosmetics, but technically not incorrect to use it either way.

if you want a dumb comparison, gacha is seen like trading card games, where power of the card also has value.

lootbox is sorta like sports cards where its collective in nature and really is about rarity/how the card looks