On the contrary, it was one of the best features. People hunting rare monsters for that lessened summon perp cost or stacking attack bonuses for special moves. In truth, there was no real 'best in slot' for a lot of jobs, and the equipment used by players was as diverse as the players themselves.
Admittedly, we could swap mid-combat but there were plenty of pieces which were good for just about every occasion.
Also, I find it amusing you consider FFXI to be 'unbalanced as hell' considering we're not exactly looking at the most balanced game in FFXIV either. In fact, the current item level system is as broken as hell with players able to power through most content simply because they outgear it by miles. An item level increase means an increase in ALL stats at once, meaning older content is now considerably easier. FFXI doesn't really have that issue unless it's specific pieces like the Relic and Empyrean weapons.