And a man who becomes unclean and does not purify himself, that soul shall be cut off from the midst of the congregation, because he has defiled the sanctuary of Hashem; the water of purification was not thrown upon him, he is unclean.
Torah Temimah: Yerushalmi Nazir 7:4
Sefaria — Yerushalmi Nazir 7:4
English: This teaches that one who requires purification (chatuy) is liable for entering the Mikdash, and one who does not require chatuy is not liable for entering the Mikdash.
Limitation of liability to those needing mei chatas.
Kares for defiling the Mikdash by entry applies to one who was obligated in the purification sprinkling and failed to do it.