Yah I can't vote in this poll because it has implied assumptions I am unaware of, then tells me to use my own standard....but by my own standard I'd use the terms "combat that is not fun vs. combat that is fun."
In Pathfinder 2E, as an example, any combat that is more than 4 CR below the group or 3 CR or more above the group will decidedly not be fun; in the lower CR case its just better to ask them how they trounce the enemy as a summary, and in the higher CR case its better to just ask them now how they try to escape certain death, than to play the combat.
In D&D 5E even really low CR encounters can be amusing sometimes, or surprisingly deadly, while some unsually high CR encounters can turn out to be unexpectedly deadly or get utterly trounced by the group.
If the definition of pointless is an encounter that does not tie in to the story or plot of the moment, then it raises questions about how to assess the concept in sandbox/hexcrawl style gaming, which is the closer style to campaigning to what I do. As a result, a wandering monster encounter is kind of the point, at times, and helps with the verisimilitude of the encounter. As a GM, the only "pointless" encounter would then be the ones players initiate for which I can't imagine why they decided to go that direction....but those tend to lean on the "wtf fun" side of the equation, being unexpected, so I wouldn't want to discourage those.