In case you've never heard the expression, "He's not the brightest bulb on the tree!" is supposed to indicate that he's not as smart as most people.
The brightest bulb on the tree. Let's look at that phrase and apply it to improv.
Does your Christmas tree (pretend with me that you have one, even if you don't) have a brightest bulb? If so, is that a good thing?
Why would one bulb on a tree be brighter than the rest? Aren't they all supposed to work together to create an overall effect? If one bulb outshines all the others, you may have a problem. It could be the wiring. Or maybe you have the wrong wattage bulb in that one socket. Either way, something needs to be done. You may need to replace that bulb with one of lower wattage to match the others. Or you may need to upgrade all the other bulbs to be compatible with the bright one.
The bulbs don't have to all be the same. Some can be blue while others are yellow or orange or red. Some can blink off while others blink on. They might not all necessarily be the exact same shape. They are, after all, individual elements.
But to have one constantly draw attention to itself and away from the design as a whole may not be the best way to go.
Extrapolate this to improvisers in a troupe. So many scenarios emerge. When audiences watch the troupe perform, should they be thinking, "Wow, Jennifer sure is funny!"? If you are part of the troupe, should you be happy to be one of the dimmer bulbs who support Jennifer's brilliance? If you're Jennifer, should you be content with that situation? Or should you find a different tree with brighter bulbs that you can be a part of?
If you're an improviser who sees a troupe perform, do you say to yourself, "I'd like to join them because I could outshine them!"? Or should you say, "I'd like to join them because I would fit right in with what they are!"?
If you're a director, do you ask Jennifer to tone it down and be more of a team player? Do you really want bright bulbs to limit their own brightness? Do you work with the rest of the team to increase their wattage? Or do you help each bulb to shine more brightly in its own way, in its own unique color? To blink in its own unique pattern?
Whatever the solution, having a "brightest bulb on a tree" is like having a "loudest musician in an orchestra." It's probably a sign that something needs to change, and that work needs to be done and decisions need to be made.