There's this really weird tendency for both the show and fandom to treat Marinette as this crazy genius while treating Adrien as a simple-minded himbo.
The reasoning usually goes that Adrichat is less intelligent than Maribug because his plans have far less steps since he's simple and straightforward, unlike Maribug's plans which have more steps and are complex and convoluted.
This is, simply told, a hollywood understanding of how intellegence works.
Anyone with experience in engineering could tell you that coming up with a complex solution is pretty easy. It's coming up with a simple solution that's the hard part.
Having more steps, being convoluted and harder to understand, and generally requiring more resources may be good for making a plan look more impressive, but say fuck all about the actual quality of the planning. In fact, all those things are indicators of worse plans, not better ones.
In the real world, 90% of the time you would want to have an Adrien on your team rather than a Marinette. (And the 10% for Marinette is mostly for her impressive divergent thinking rather than for her complexity addiction.)
And there's actually an episode that demonstrate everything I just said.
In Kwamibuster, Marinette and Adrien are both faced with the same problem. Their kwamis showed up together at their school, which gives their superhero partner a clue about their identity. Both of them have to figure out a way to protect their identity from the other.
(Fun fact, while Marinette realizes this must mean Chat goes to her school, Adrien almost immediately goes to thinking Marinette must be Ladybug. That boy has a consistent pattern of figuring out who Ladybug is from even small clues.)
Since they're both faced with the same issue, we can compare the way each of them approaches problem solving pretty easily.
Marinette cooks up a scheme that includes three miraculous, a grand illusion and running a con on Chat Noir. She ends up giving herself a strong alibi that Marinette can't be Ladybug, as they were seen together.
Meanwhile, Adrien merely says:
Cat Noir: Ladybug, wait! I wanted to apologize for my Kwami. I don't know what he was doing in that elementary school. Ladybug Illusion: It was a high school. Cat Noir: High school, right! I'll promise it'll never happen again.
And instantly debunks the idea that he learns in that school or even anywhere near it.
So what we have is a complex plan that took a lot of resources and only managed to clear Marinette (since she did nothing to debunk the idea she's studying in that school) vs a simple plan that only required saying a single line to debunk the idea he knows that school at all. The difference between the effort-to-reward ratio is insane.
Adrien's plan here is clearly the better one here. It's both more effective and doesn't require three powerful magical artifacts in order to work.
The simplicity of it isn't a sign of stupidity, it's a sign of cleverness. If you don't believe me, I challange to think up a different scheme that the heroes could have used to cover their tracks, only one time you're allowed to use three of the miraculous Marinette had access to, and the other time you're only allowed a single line as an excuse. The first is far easier to do than the second.
And Kwamibuster isn't the only time we see Adrien being clever in that simple-but-effective manner. In Zombizou he hides in his locker and pretends to be a zombie so he could get away and transform without anyone asking questions. In Antibug he easily traps the akuma by making only the ground under her feet collapse. In Volpina he prevents Ladybug from surrendering the earrings without exposing himself by dispersing the illusion. In Truth he outmeanuvers the truth spell by realizing he could ask questions of his own rather than letting the akuma ask.
Some of those are things may seem obvious or unimpressive, but that's the nature of those kinds of solutions. As soon as you see the answer, it seems obvious. However, actually thinking up that simple but elegant solution is the hard part.
Marinette and Adrien have different approaches for problem solving. Just because Adrien's doesn't make a spectacle the way Marinette's does, doesn't mean he's dumber.
