While Arixmethes may still be tapped to produce mana once it's no longer a land, when there are no clumber counters on it, Arixmethes is a 12/12 that is able to pose a serious threat to your opponents
The bounce package has been a key component to a number of tier 1 decks, including Amethyst/Ruby Control and Amethyst/Emerald Tempo decks
As part of the 99, its still reasonable as a late-game threat
The likes of Jade Bearer, River Heralds Boon, and Deeproot Elite help it become a 4/4, 5/5, or 6/6 threat that you cant target for removal
The next time my creature would be destroyed, it isnt
Once a great blue staple in graveyard decks, its since been passed over by the likes of Consider, which just gives better options when it comes to putting cards into the graveyard (altough it's still unmatched among the most disturbing pieces of Magic art)