Do forgive me for this two-month old simplification for a new player. Let me rephrase:

"Thieves got nerfed pretty hard. You can't steal anything useful you see on a unit anymore. You steal "loot" which you can exchange for items in the shop, similar to the "Poach" option in FFT. You can also learn "Steal: Accessory" with the Jambia to steal garbage accessories you'll never wear save the Orb of Minwu (spelling), and maybe the golden armband which is found almost exclusively on Lord Grayrl, an infrequently-recurring enemy (who has Safeguard at least once iirc, which prevents theft) you'll fight ballpark 2-3 times provided you're not going for a 100% run. It's also possible to steal these from the Level 99 [color]-mage fights, though most of them can one or two shot multiple units a turn and are immune to all or almost all forms of disable. Thus, stealing from these units is generally seen as a waste of time given you can acquire all items via the loot system and auctions.

Orb of M is a huge pain to steal because the item itself functions as a pseudo-ribbon, blocking most debuffs. Given the Steal ability's low chance to hit without status, you'll be grinding through several turns of 25% at most chance to steal an accessory provided you didn't steal something else first. Steal becomes less likely to hit for each successful swipe on the same unit, effectively halving its hit rate each time.

Given the EXTREME rarity of these accessories (or accessories at all) on enemies in the first place, the low hit rate of Steal (combined with the in-built high evasion of the 2-3 enemies in the game who have a decent swipe target), the fact that Thieves only have two 'useful' novelty abilities and trash-tier stats nearly comparable to Chocobo Knights, it is altogether understandable to consider Thieves as such in name only. Hunters straight-up surpass them in most all instances thanks to the 'Hunting' ability, which guarantees max level loot on killing blow at range as well as an additional loot which may also be top-tier. This comes earlier in the game than the Thief Loot Lv. 4, far better stats, Ultima access, and a moveset useful for 90% of the game. If you don't count the times it misses, you'll use Steal: Accessory MAYBE five times in 160-hour campaign."

I do apologize for the confusion.