Before Fortisphere was banned, more than half the competitive players were using Sapphire-based item decks, making it impossible for other play styles to flourish
You can, however, use them for synchro summons, tribute summons, or just to activate this cards effect
This monster has 3750 attack points (even stronger than Blue Eyes White Dragon) and the duelists use cards like Fairy Meteor Crush to deal piercing damage
Not every deck is going to want Ionoa, but those that do will really want her
Even if you can only keep this card on the field for a turn or two, preventing your opponent from Special Summoning for a turn gives you a significant edge in the duel
A fairly common build for this style of deck is to only run massive creatures like Eldrazi Titans in your deck while playing spells that can create tokens for you to sacrifice