I don't think anyone is suggesting that trauma isn't real, or that people can simply decide not to be traumatised. Trauma can have a profound impact on how someone thinks, feels and behaves, and healing often takes years of work.
My point is slightly different: acknowledging trauma and understanding its effects is important, but making victimhood your identity isn't the same thing. Trauma may explain some of our struggles, but it doesn't have to define who we are forever.
Likewise, some people are undoubtedly privileged to have grown up in stable, supportive environments and therefore start life with advantages others don't have. But recognising that privilege isn't the same as believing people are powerless to heal and grow beyond what happened to them.
Trauma shapes us, but it doesn't have to become our entire identity.
The other thing I'd add is that "well adjusted" people are often not as well-adjusted as they appear. Some genuinely had easier starts in life. Others are carrying their own wounds but have different coping styles, better support systems, or simply hide their struggles more effectively. So I would be cautious about assuming every apparently well adjusted person is merely benefiting from privilege.