I think this depends on what you mean by "JLA" power level. If you mean -- what they are most likely to do with the characters most of the time in stories and cartoons, then perhaps. I would guess many games are actually closer to what Avengers characters can do, though.

*Account for various combination of superpowers, or their lack.  More than many other genres, you need to account for "Oh, the central conflict of this adventure is something I regularly resolve in my downtime."  Murder mystery? Needs to deal with super-science, super-senses, necromancers, reanimators, and many more things.  So, you'll need a pretty strong understanding of the underlying system, and what is and isn't possible, in order to make the adventure feasible.

*Absolutely no "Your powers don't work here!" areas.  They're tedious and played-out.  What are fun are "This villain or scenario has these effects, here are some interesting ways they interact with other power sources in the setting."

*Strongly-characterized NPCs.  This, I think, is probably the most important part of any module; in my experience, PCs are far more likely to stick with a module and care about the outcome if the people they are interacting with are fun and interesting, and if they want to keep said people around after the adventure is over, you've got build-in sequel hooks.

*Good (but not overwhelming) ties to the existing setting / metaplot.  Most games will at least gesture in the direction of the existing setting, so having things that tie into that

One of the favorite extended modules that I ran for my group was for Mutants and Masterminds 2E, called Time of Vengeance.
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3. Bring the Dungeon!: what I like from many of the V&V modules is at some point the PC supers have to infiltrate the BBEG's HQ, which brought a 'dungeon-crawl' kind of experience that connected to my D&D play.

4. Media Attention: the PCs' public activity should find its way onto TV, radio, newspapers and the web. Maybe the heroes are portrayed as heroes or vigilantes or criminals or a combination that impacts how NPCs react to them.

Regarding buy-in, I've had good luck with players telling me why they're bought in.  In the last supers game I ran, I told the players at the beginning, I needed to know what their opinion of the main NPC was.  I didn't care if they loved him or hated him, they just couldn't be neutral.  That way, they'll care one way or the other what happens to/with that character.  Tell me why the Midtown Museum is important to you.  Everybody knows Det. Kwan hates supers -- how did she mess with you?  Stuff like that.

When I'm making a supers adventure, I try to make sure I include a problem they can't punch their way out of.  Something they'll have to think their way through.  Not to make their powers useless, but make them get creative.

Something I'm not always good about is keeping up a sense of urgency.  Don't let the PCs plan like a SWAT team.  If they don't move, the bad guys hit somewhere else.  If they take too long, they hear about the bad guys making a major score they *know* will be bad.  Keep them moving and keep them on the clock.

It is generally agreed that JLA characters are a lot more powerful then Avengers characters. So much so, that I often point to the difference between them to illustrate the difference between Cosmic Tier characters and Planetary tier characters when I am talking with players of my system.
An easy example is the Flash and Quicksilver. They are both speedsters, but the kinds of things they can do with their speed are not really comparable.

I don't personally find that comparing the most ridiculous thing that a character has ever done to be useful, but what they do routinely still points to this.

This could easily become a thread derailment, so perhaps I will leave it at that.

Almost_Useless is saying something similar to what I'm trying to say.

Sub-Plots.

Superhero games, in the end, are not about "leveling up".  They are about pursuing stories the players want to pursue, in ways that are interesting.  The Sub-Plots are what the superheroes are speaking directly to our psychology, and that is ultimately what the genre is all about.

"My guy can beat-up anything and always wins" is a child-like, personal fantasy that will grow old quickly, IME.  It's the problems that still exist, and how they are resolved, despite god-like abilities, that makes the Super Hero genre popular.

It was, LITERALLY, what Stan Lee is famous for.

I realize this can be tough for a module.  Maybe you can generalize to a level that will reach across groups?

Ex. Romance Subplot:  Character A's love interest does B, and X happens to them in Scene 3.

Self-Doubt Subplot: ....

Outlaw Subplot: ...


Etc.


Let's face it, most of these fall into broad-strokes categories.  You can give the GM plenty, and still let them customize it to their group.