I doubt that people were asking for the train to come back because they wanted to afk, but because they wanted something at least slightly fun and intresting to happen within this mindnumbingly boring content.
Chain killing mobs has two main problems for me: Its boring/not fun AND it feels extremly unrewarding, given how little you gain from it (exp, light) and how much you need.
Without the challenge log, an hour of mob chaining makes me feel like I got nothing for that and wasted that hour. NMs were a great thing to combat that in Anemos, because you got all those "mini"-goals on your way to reach your main one.
I dont need my weapon handed to me on a silver plate - I completed 3 relics from ARR-start to HW-finish, cleared some Savage, got both freaking Yokai-mounts, I even played PvP when queuetimes were up to 2h+ and got my rank to 50 back then.
But what I need is something to keep me engaged in this content. Chaining mobs isnt doing the trick. I need to leave Eureka with a feeling off "I really made some progress today and got something out of it!" Even if that something is just a tone of lootboxes.
My boyfriend and I hated Eureka and only went into Anemos once they added the challenge log. As soon as our levels were high enough we joined the train and spend a lot more time in Eureka than we expected, because of the classic "Just one more episode!"-feeling - in this case thats obviously "Just this next NM! Numbers is up again in 10 minutes, we can wait that long!"
We actively helped spawning most NMs and having the boss appear was always a nice reward for slaughtering all those things.
I dont want to afk in Pagos - right now I dont want to go in there at all though.
I dont need stuff handed to me, I need stuff to feel rewarding and they tanked that on so many levels: Slow progression, weapons that are outdated, less "cheap" rewards like lootboxes, depending on your job not only an outdated, but also ugly weapon (I main a paladin...)
In its current state, Pagos is not only not fun, but also not rewarding. Fixing NMs is a step in the right direction.