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

[Havenchild]

I honestly think ninja gives more of a mind fuck than summoner ever will lol (to play optimally)l. All that situational context you just gave though is a every job in ffxiv kind of thing. it's not like we all play on scripts lol

Again, do it before you can dismiss the difficulty. Considering you've downed T13, you should have enough knowledge to play a SMN properly since to you it's bread and butter. Now do so, and pull as high as your BLM. Come back with some parse comparisons of you're own and tell me it was as easy as your BLM to reach those numbers. Promise you it will blow your mind.

I'm by no means an absolute expert on all of those jobs though.

Oh, that's why it seems easy to you. Makes perfect sense.