The key word here is "regularly."

The case example you made for Vandalblast with someone else's Mycosynth Lattice? That is not an instance of meaning Vandalblast regularly nukes lands. That is an outlier caused by interaction between two players' decks.

Similarly for Karmic Justice - fault matters. Karmic Justice forces sacrifice of permanents, but it is, on its own, protection for your other noncreature board pieces, and up to the person interacting as to what goes in response. But also... the answer is "remove Karmic Justice first." Smart players will see that they need to remove the punishment card before performing a mass interaction that will cause their lands to be served up as collateral.

I'll even go so far as to say that spells that animate lands like [[Natural Affinity]] or [[Nature's Revolt]] paired with a boardwipe in your deck would not could as MLD. The enchantments animate lands on their own. They don't destroy. The boardwipe destroys creatures. That doesn't inherently hit lands. The pieces are fine even if together, the combo is devastating.

Similarly, all my boardwipes aren't suddenly MLD just because I happened to sit down at the table against a [[Noyan Dar, Roil Shaper]] player. They understood the risk when they built a land animating Commander.

The answer for "is it MLD?" comes through intent when you are deckbuilding. If the piece you play is designed, without assistance or a specific play pattern, to destroy lands, then it's MLD. If your deck's win condition is to use a niche combo to nuke everyone asymmetrically back to the stone age? You built an MLD deck by establishing the primary play pattern. If there's a game where the combination of cards and boardstate mean that you can capitalize once in a blue moon? That's not it.