Can someone give me an in-depth explanation why Summoner is arguably the worst DPS?

[Romsca]

I gain Piety when I use my BLM soul Crystal, Summoner Don't. BLM don't have a flaw design. They don't need to be changed so they are equal to SMNs. It's the SMN that needs to be changed meaning you are saying they need a buff.

All classes gain mana for each point of piety. Each class and job gain it at different rates. Blm and smn have zero piety on gear outside of crafted gear and food. What I am saying is that for smn, with a base amount of 214 piety, our conversion rate should be way higher than blm to the point that without crafted gear or food smn should be sitting around 4k mana pool.
Blm does not have need for a large mana pool, having one is a perk. Your class mechanic is to swap though fire for damage and ice for regen, rinse repeat. Summoner doesn't play that way. Every class has a form of resource replenishment. However, not counting bards songs, no class can sustain infinite resource like black mage. Even melee run out over time. So smn should receive a higher mana pool so aetherflow returns more back thus extending our staying power, increasing dps with more festers, and strengthens our class playstyle of being a multi target dotter. This small mana fix also changes spell speed to be favorable for smn.