When I started playing....
...Glamours were locked until level 50
...Glamour prisms weren't consolidated into a single type; there was one each for Woodworking, Blacksmith, Carpentry, etc. (I believe before that they were divided into several different grades too!)
...Glamour plates weren't a thing.
...World Visit wasn't a thing.
...You couldn't have a minion and your chocobo summoned at the same time.
...You couldn't increase your chocobo's summon time to 60 minutes by eating more than one Gysahl Greens.
...The chocobo saddlebag wasn't a thing.
...Stacks of items were limited to 99 instead of 999.
...Swimming in Costa Del Sol or the residential areas wasn't possible.
...You couldn't use aesthetician hairstyles on retainers.
That's all I can think of off the top of my head.
