Tortles are awesome! However, 5e doesn't do a great job making them interesting (as others have brought up, I've never liked them being a short-lived race).
In my games, I have a subrace/variant of Tortles that are more like Turtles than Tortoises, they trade their claws for a swimming speed. I also have a sub-culture of Tortles that live
inside lakes in underwater houses on the floor of the lakes made of a sandy-concrete material, and they have tubes that go up to the surface that they can suck air out of (due to the fact that Tortles can hold their breaths for 1 hour underwater, they only visit these once an hour and sleep with face-masks that let them breathe. The Tortles spend their days walking at the bottom of the lakes for protection from land-animals (typically dinosaurs), catching fish in nets, hunting Plesiosaurs, and using tamed Giant Crabs as beasts of burden.
And, yes, Tortle Monks are kind of the default, due to the Teenage Mutant Ninja Turtles and Master Oogway. However, I also quite like Tortle Rangers (with the Druidic Warrior Fighting Style for Shillelagh as a TCoE Beastmaster Ranger, you can have a Giant Turtle/Tortoise animal companion and be a Wisdom-focused melee-ranger with a Staff that wanders the world), Tortle Druids (Moon Druid to turn into Giant Snapping Turtles and can eventually use Shapechange to turn into a Dragon Turtle), Tortle Barbarians (Path of the Beast with the Bite attack to be a Snapping Tortle), Tortle Clerics (
Krull is awesome! As are Tortle Tempest, Nature, and Peace Clerics!), and Tortle Sorcerers (Draconic Bloodline to be a Dragon-Tortle).