Herein is the problem (for me). My group gets together twice a month, if we're lucky. We get about 3 hours of "quality" time each session (after taking out breaks, snacks, general socializing, etc.) Knowing that the majority of our time is going to be spent with "another ho-hum goblin encounter that will only challenge us by spending a 1st level spell and a few arrows" or a trap that might do 1-6 hp of damage, it just doesn't seem a good way to spend time.
So, you are doing it wrong, even by the resource depletion model of challenge. The resource depletion model is how challenge is created in traditional D&D. It cannot perforce be assumed that that is how fun is or ever was created. Challenge is only one of several pillars that fun collectively rests on, nor is resource depletion in any fashion contrary to the other pillars.
What you are talking about is not a failure of "resource depletion" but a general failure of encounter design.
Let me deal with the trap first because it's the most obvious problem. As a general rule, your trap design is bad if:
a) The trap does not seriously threaten or impede the party and the trap is a standalone encounter unassociated with any other encounter.
b) The trap delivers a big burst of damage instantaneously but does not put the party into any other ongoing difficulty.
So it wouldn't matter if the trap delivered a 6d6 damage fireball, if the trap was just isolated on its own then this is a non-encounter and terrible design.
Good traps on the other hand:
a) Deliver ongoing damage or otherwise place party members in ongoing jeopardy.
b) Require party members to work together to extricate themselves from the difficulty.
c) Occur as a hazard as part of some other ongoing difficulty, such as within the context of a fight with goblins.
So a 20' pit trap which when it activated, also rang a gong which summoned goblins to attack the party is a well designed encounter. There is a problem - some party member is down in a hole while a fight is going on - and there is some sort of progress to the encounter. Perhaps the goblins arrive in a series of closely packed waves that utilize different weaponry. Perhaps at some point this encounter is going to encourage the players to maybe flee to regroup, but they are hampered by the fact that someone is down in a pit and can't retreat.
If the encounter is "ho hum" regardless of whether it represents a serious challenge on its own or simply depletes some resources, it's a badly designed encounter. Period. Make your encounters unique by varying the terrain, the weather, the encounter distance, the weapons, the tactics, the goals of the opponents, or introducing three party conflicts with an opportunity to potentially ally with one side or where the PC's may wish to rescue the third party (the goblins are transporting slaves in cages on carts, pulled by wolves, and guarded by outriders on wolves with bows with arrows coated in vegetative poison that inflicts some condition on the target). There is never any excuse for a boring encounter.
That out of the way, if your group only meets irregularly you have to decide what your group prioritizes as fun. If your group really likes to RP, make sure almost everything you do involves some potential RP. Combat doesn't need to be the focus. Or if your group likes dungeon crawling, then make sure you spend a lot of prep on making your rooms original and interesting with different types of problems of exploration, puzzles, combat, and role-play. Or if your group is into wargaming, make sure that the encounters are tactically diverse.
I really don't see this as an issue that 'resource depletion' has much bearing on at all.