There are a lot of varying opinions on how complex flags should be. Some prefer that flags be kept more simple and minimal, and others feel that simple flags come off as bland, corporate, and unflaglike. What do you think?

My take is that complexity on flags can be great given the following:

• Complexity is used to make a specific a focal point stand out. Flags aren't paintings and shouldn't be littered with complex designs. Instead, the complexity should be focused in the flag's device.
• Complexity is in shape, not in color. If a flag has 6 different colors in its device, it just ends up feeling cluttered imo.
• Complex images are unique and symbolic. In general, devices should be symbolic, but imo both it and distinctness is especially important if you're going to draw extra attention to it with a complex design.

One of my favorite flags, the flag of Bhutan, does all of these with its black and white dragon.

Nevertheless, I don't think flags being minimal or following more modern design principles makes them soulless and corporate. Simple designs can look great, and I honestly tend to prefer them. Just because logos tend to use more simplistic designs doesn't mean flags can't either.