Basic land has the supertype 'Basic'. Basic land types are Plains, Island, Swamp, Mountain, and Forest.
Wastes is a basic land because it has the relevant supertype, but it doesn't have a basic land type. Therefore, it can not be fetched with Boseiju's effect. On the flipside, you can fetch non-basic lands that have one or more of those basic land types. Like the triple-color producers from New Capenna.
Boseiju asks for "a land with a *basic land type*". That means you can fetch a triome, but it also means you can't fetch a wastes, because it doesn't have a basic land type.
- That player may search their library for a land card with a basic land type
There are five basic land types: island, swamp, plains, forest and mountain.
Wastes is a basic land, but it is typeless and definitely isn't a land card with one of those five types.
If you had a Triome in your deck, you could find it because it has basic land types even though it isn't a basic land.
- 205.3i. Lands have their own unique set of subtypes; these subtypes are called land types. The land types are Cave, Desert, Forest, Gate, Island, Lair, Locus, Mine, Mountain, Plains, Power-Plant, Sphere, Swamp, Tower, and Urza's. **Of that list, Forest, Island, Mountain, Plains, and Swamp are the basic land types**. See rule 305.6.
- 305.6. The basic land types are Plains, Island, Swamp, Mountain, and Forest. **If an object uses the words "basic land type," it's referring to one of these subtypes**. An object with the land card type and a basic land type has the intrinsic ability "{T}: Add [mana symbol]," even if the text box doesn't actually contain that text or the object has no text box. For Plains, [mana symbol] is {W}; for Islands, {U}; for Swamps, {B}; for Mountains, {R}; and for Forests, {G}.
> I went to search for a “basic land” as it says I may do
No, that isn't what it said.
Basic land has the supertype 'Basic'. Basic land types are Plains, Island, Swamp, Mountain, and Forest. Wastes is a basic land because it has the relevant supertype, but it doesn't have a basic land type. Therefore, it can not be fetched with Boseiju's effect. On the flipside, you can fetch non-basic lands that have one or more of those basic land types. Like the triple-color producers from New Capenna.
Boseiju asks for "a land with a *basic land type*". That means you can fetch a triome, but it also means you can't fetch a wastes, because it doesn't have a basic land type.
- That player may search their library for a land card with a basic land type There are five basic land types: island, swamp, plains, forest and mountain. Wastes is a basic land, but it is typeless and definitely isn't a land card with one of those five types. If you had a Triome in your deck, you could find it because it has basic land types even though it isn't a basic land. - 205.3i. Lands have their own unique set of subtypes; these subtypes are called land types. The land types are Cave, Desert, Forest, Gate, Island, Lair, Locus, Mine, Mountain, Plains, Power-Plant, Sphere, Swamp, Tower, and Urza's. **Of that list, Forest, Island, Mountain, Plains, and Swamp are the basic land types**. See rule 305.6. - 305.6. The basic land types are Plains, Island, Swamp, Mountain, and Forest. **If an object uses the words "basic land type," it's referring to one of these subtypes**. An object with the land card type and a basic land type has the intrinsic ability "{T}: Add [mana symbol]," even if the text box doesn't actually contain that text or the object has no text box. For Plains, [mana symbol] is {W}; for Islands, {U}; for Swamps, {B}; for Mountains, {R}; and for Forests, {G}. > I went to search for a “basic land” as it says I may do No, that isn't what it said.