The BBC would have the church promote whatever makes people in each time and place feel warm and safe. This appears to be Archbishop Welby’s approach, too. But this has never been the Church’s mission. Jesus was not crucified because He made everyone feel warm and safe.
The societal influencers feel constrained by the created order of male and female and encourage people to express their uniqueness. Teens in general, and teens with existing mental health issues in particular, will be especially vulnerable to these pressures.