During the night on both creative and single player,pilagers fail to spawn in at outposts along with hostile mobs failing to spawn at night. Does not seem to effect illagers in mansions .
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Also no basements spawn in igloos.

You are in peaceful mode. Most hostile mobs despair in peaceful, and one that don't won't attack you. Also igloos have a 50/50 chance to have a basement.
Was on normal mode not peaceful.
in my survival world the same

How many days have you had this world? The more mobs in an area, the slower they Spawn. For the pillagers, has this world ever been in peaceful mode underground or when you where near the outpost. Pillagers don't resawn to my knowledge but I might be wrong.

Clarification: by the more mobs in an area, I mean it's possible there are a lot underground.
duplicate of this bug: MC-139338