I think someone else already answered in a past thread but can’t remember. Everything is playable solo, with AI companions for the group stuff, correct?
This is correct.
Main story is 20-25 hours. I guess there is some postgame stuff(I think character specific quests where each character has 10 or so?) that pushes it to 30-35.
Sidequests, grinding/upgrading characters and whatnot pushes to 100+ hours.
I assume most sidequests are repeatable with friends or for stuff you grind for so tons of replayability.
Also factor in you have 16 different characters to level/grind/upgrade and I think level cap might be 100 or something so definitely a big game.
For reference the single player campaign of Dragon's Dogma was 37ish hours but over a 100 with replaying the game and not to mention the Black Isle.
For previous P* game lengths you have Astral Chain at about 20 hours(which doesn't include it's postgame stuff which is pretty huge with it's 71 Arena fights), Bayo 1 was like 12 hours, Bayo 2 was 9 hours, Nier Automata was 21 hours, Vanquish 6 hours.
I'm not concerned at all. If anything Granblue is probably one of my most hyped games for 2024.