I don't know if these are really fair comparisons or criticisms.

Yes, the Pale King's plan went sidewise, but it would have worked, and Hollow Knight (the game) proves it. It didn't work because of a fatal error by the Pale King, that being treating the Hollow Knight like a beloved child, rather than an empty vessel, introducing "impurities" into its being.

The Infection also isn't a result of the Pale King's plan. It appeared before the plan, and is why the plan was conceived at all. The Infection as seen in-game is what would have happened had the Pale King done nothing at all.

He didn't so much make things worse, as he did delayed the inevitable. Had he succeeded, his Kingdom would have survived, while failure was the same as if he had done nothing.

Hornet does try to act like she didn't expect a plan devised by snail shamans (that she knew were snail shamans) would involve the abyss, but the plan ultimately failed because Lace got involved. I wouldn't really put that part on Hornet, though it is true that enacting the plan was her choice, and it definitely made things worse, regardless of any unforseen flaws in said plan.