Humor also depends on the mindset of the people at the time, which is why something written in the 80s may not seem as funny to someone who grew up in the 90s. There's really not a significant difference between that Maxx panel and one from She-Hulk, it's either more or less funny to the reader.
Some humor is timeless but it's still a pointless task to try to distill why people think one thing is funny and not others.
For example, this panel was written dead serious. It's not a gag, but it's hilarious to me.