For terms of complexity. The game is more or less the most basic and simple AAA mmo on the market.

Gear has no unique stats, Jobs have no unique builds, progression is pure linear (the game goes in a strait line more or less progression wise). No real supporting roles for jobs (Br/mch is not a support class). no resistance and weaknesses. Game is ultra simple from start to end.

As for easy. Well that explains everything except the most current endgame raid.

So by that default the game is extremely on the ultra easy spectrum. Although complex vs easy is not really a good argument. THe game could be piss easy and ultra complex, Example ffxi outside 2 bosses the game was easy mechanics wise but everything else pre-abysea was ultra complex with a jobs having multiple party roles, builds, and gear sets. Hard vs Easy would be a better comparison.