Wyatt is one of the dumbest characters ever on screen (Spoilers)

I agree. I liked his character in the first seasons. He seemed thoughtful, conflicted, and loyal to his family. But then he just turned into a warm body making the same exasperated and confused faces and mannerisms in every scene. Its like they ran out of ideas and kept him around to kill him for the climax.
I guess his character is supposed to be drawn as kind of a timid puppy. In that way its plausible he'd be attracted to strong personalities like Darlene's. He comes from a family of strong, brash types (like Ruth) and Darlene probably seemed familiar and safe in that way. Plus he likely has mommy and daddy issues. So in that regard I'll give the writers room for him and Darlene s relationship. She's probably attracted to him because he's easily controlled and she can demand full loyalty. Like a codependent relationship.
But still his character didnt have much arc and his scenes were mostly repetitive and luke-warm.

Not to mention instantly falling for the 'child services are gonna take my baby' bs and not checking into it.

Hey, they fucked EVERYTHING up in S4

Wyatt and Darlene were both stupid as fuck for ignoring the Mexican cartel that flat out told them that they would kill them if they keep selling.

They didn't even have security posted or behave like extremely dangerous people were out to get them. And Ruth somehow still blames Marty for that predictable outcome.