tooltips do not explain how wall to wall pulls work.

Tooltips do not explain how to differentiate between magical and physical attacks. Example. P1S the bosses aoes are physical damage not magical.

Tooltips do not explain how mitigation works or how it stacks.

Tooltips often do not explain how abilites interact with other abilities of the same class or other classes.

Some tooltips are misleading. Example: Before DRK QOL in 6.1 Bloodweapon duration stated 10s when it was actually 9s

It is extremely important to read tooltips but they do not explain the whole story and even with some players playing content they wont understand until other players explain it to them. However the same time FFXIV has many job changes yearly including tooltips so its hard for them to develop a hall of intermediate or something that can assist players because it would require constant upkeep.