3.15 relic will require items that randomly drop from the following mobs:

[RiceisNice]

Actual meaningful relevance to the storyline and the weapon itself. Not rehashing grinding steps to FATEs.

The original relic went down hill from Atma and onward;

Atma led to no item upgrade despite arguably being the most tedious of the steps for the drop rates (and the godamn npc telling you got stronger anyway despite losing it's glow)
Animus specific FATEs, I swear they purposely have these spawn less frequently compared to other FATEs within the region, and opted out popular areas such as N.Than and E.La as atma areas.
Novus I can't really complain about, it was a slow but-sure procress, and materia was the only thing that would vary with the sucess rates.
Nexus light grind...bleh it gets incredibly tedious and amounted to trial zergging.
Zodiac would have been fine if i weren't for disregarding the entirety of the relic weapon lore (especially for BRD imo)
Zodiac Zeta rehashed nexus light.

All the while, the "lore" behind your weapon comes to a complete stop after the initial quest, and really loses out the novelty of it being your weapon/legend when you're doing the exact same step and dialogue for all your upgrade steps (animus books for example, apparently all zodiac heroes of days past went and defeated modern day garleans)

[Dualblade]

snip

Just gonna say for the Animus fates, they were specifically chosen because not alot of players were doing them, which is also why N.Than and E.La didn't get them (as they were popular areas.)