If you create characters like Collector and Grandmaster and make them dead serious you miss the point. Collector is the guy who keeps a talking duck in a suit in a glass showcase. You can't make thoe characters serious.
You also can't undermine them dramatically too much either. In the original comic of the Infinity Gauntlet story you for sure are supposed to understand the awesome power and cosmic majesty that is being arrayed against Thanos when the various universal powers from the Elders to Galactus to the Celestials confront the mad Titan.
When you do something like take them too seriously as, making Galactus a poo cloud as in the Story FF movie because the studio or the director thought a giant humanoid in space armor was too easily mocked or absurd, yeah that undermines the essential character by making it something far different than the original comic... Highlighting the inherent absurdity and turning them into camp though, and I would argue that is what they did with with the Collector, can also undermine the characters, especially if there s plans to use them in a later film like IW.
And as always, my response to the idea that you shouldn't have seriousness as the floor when handling these characters for the most part is... As kids when we were introduced to these universes we took them very seriously. Enough so that they did not fade in our psyche as something merely for children.
Of course in comparison to our real world it's all absurd, and you can't weight these ideas down with "logic" to the point that they cannot soar under the banner of suspension of disbelief, but as I see it, suspension of disbelief can also be pierced if you only take the absurdity at face value, present it as such and therefor drain the stakes and drama.
There is a great line from THE FIRST AVENGER that Zola says to Tommy Lee Jones' Col. character that sums this up for me. After Zola reveals the Skulls plans the Col. responds:
Col. : That's crazy.
Zola: The sanity of the plan is of no consequence.
Col. : And why is that?
Zola: BECAUSE HE CAN DO IT!
All stuff in super hero stories is bat-guano nuts. Most villain plans to "take over the world" would fall apart upon further examination. But in reading the stories the presentation has usually been that as out there as any of it is you are supposed to buy it all really happening under the umbrella of suspension of disbelief. Do too much to draw attention to the absurdity or illogic and it can in my mind really reduce the impact and experience of the story and characters. None of that precludes humor n any way but it I think it shows that the focus should be on making and action adventure story featuring heroic characters, not injecting humor to the point of collapsing the belief in what is going on in the story.