Hi, I played back when it happened so here's the story.
Our main stats include Strength, Dexterity, Vitality, Intelligence and Mind. Amongst these used to be Piety, which is now a Role stat restricted to healers.
Melding a main stat to gear that already had this main stat was pointless - because it was already at the "stat cap" for that gear piece. The game did not used to tell you the cap either.
Only certain main stats are relevant to certain jobs:So think about that for a moment. What if a casual player melds Piety on a Dragoon (that doesn't use MP at all)? What if a casual player melds Strength to their left side gear that is already capped on Strength?
- Strength is for melee DPS (excluding Ninja/Viper) and tanks.
- Dexterity is for ranged physical DPS (Bard, Machinist, Dancer) and Ninja/Viper.
- Mind is for healing spells (so, only affected healer heals or anyone that could access them - at the time, Paladins could cross-class Cure and Summoners had Physick inherited from the same class as Scholar). Did not affect healing spells of non-healers.
- Intelligence is for caster DPS (but used to increase healer DPS because healers swapped Mind with Intelligence via Cleric Stance; this was changed to be just Mind for both instead when Cleric Stance was removed).
- Piety increased MP (it didn't used to be a universal 10,000 like it is now). This was not useful for jobs that didn't use MP, and was often not used for ones that did either. Jobs other than healers using it would see them laughed at, and healers were split on what stats they used.
Among the good players who used them properly, these melds were mostly used on right-side (accessory) gear. Why? Because these did not used to have certain main stats on them that the other side had.
For example, tank accessories had Vitality instead of Strength, pressuring tanks to meld Strength to increase their DPS or flat out use melee DPS accessories. This caused a huge war with the developers, who in Heavensward had to make Vitality increase tank damage to make them even care about Vitality. In Stormblood, they stopped allowing tanks to wear DPS accessories, but some of them continued to wear Heavensward ones! So they decided to add Strength to tank accessories, which made them pretty overpowered in old dungeons (this was the start of us really destroying old content and it becoming a joke, aside from potency increases and item level gains). We still melded Strength to take it near cap on accessories.
There was also a lot of confusion among non-tank players over what to meld. While they could meld DPS substats, some players chose to meld Vitality to increase HP and survival in raids.
So in Shadowbringers, there was a giant overhaul:Like virtually all changes, the way it was before, it was a joke/a meme/pointless and only served to confuse or trap new players that didn't know what they were doing. As the above poster said, changes like this made the game more straight forward and reduced to pitfalls for new players - at the cost of making it feel like it lacks depth. But as I said, that depth was more of a pitfall than actual depth.
- All gear for all roles had the same amount of stats on their respective left and right sides.
- All gear, including the right side, was capped on Vitality and the main DPS stat.
- Tanks were made to have more endurance via a trait instead, which bakes in the 20% damage reduction they had on their tank stance, increases the effect of the Vitality stat, and reduces the effect of the Strength stat (since tanks are meant to do less damage in exchange for more endurance).
- And of course, melding main stats was scrapped as a concept since, beside the examples I gave, melding most of them would see you laughed at or be meme'd upon.