I find that the fact that we see her trauma every step of the way rather keeps it from being a trope. We've had several male characters have difficulties dealing with what they've been through in the MCU already. To not have a woman also represented would be a problem.
Okay, I just re-watched the last ep of WandaVision.
I must have missed the final post-credits scene when I watched it first time, because I have no memory of it. Not that it really changes how I feel about Wanda's suddenly becoming a homicidal maniac. Yes that scene hints at Wanda dabbling with Forbidden Things. But... so what? That scene, with some oft repeated lines about "the Darkhold is Bad, mm'kay" comes across as inadequate motivation for Wanda's
extreme change. And that, the failure to give justification equal to the character's change, is why it feels like a lazy trope. Look, it's clearly a case of YMMV. I don't object to Wanda going bad. I object to the way in which it was done in MoM.
Regards not seeing any of the MCU's female characters have trauma responses when several of the male characters do, I agree that would be poor. But, as
@Davies has pointed out, Wanda's response to her trauma, and the come-uppance she gets given, are written dramatically differently to those written for Hawkeye, Thor, Strange and Stark. Also, let's not forget Black Widow. Or Captain Marvel's arc in her first movie. Or Wanda in WandaVision. There's plenty of women with trauma there.
I'll just finish with I enjoyed MoM. It was dumb fun. Exactly what I expect from Sam Raimi.