Let Us Go On To Maturity - HEB 6:1

Therefore let us leave the elementary doctrine of Christ and go on to maturity…
HEB 6:1
Life is a journey, and like any other journey, there is a beginning and an ending. We begin the journey of life at birth, and we understand that the event of death is a future reality. Physical life is a journey of experiences and learning. It is a journey of growth, hopefully leading to maturity.
There are many ways by which we define maturity in society. Somehow, it normally assigns a certain responsibility or capability as the defining point. This capability can be associated with a certain age number therefore associating maturity with time. Here are some ways we define maturity as a society in the Philippines.
We are given capability to elect the leaders of society at age 18
We are allowed to marry by age 18 as long as with parents’ legal consent, but freedom to marry is at 21 years of age
Parents treat their children as mature once they finish a degree and begin to work for a living
Of a definite consequence, maturity involves outgrowing some things. To outgrow is to leave some things behind because a more appropriate replacement is already in place. So, a full-grown person cannot wear his child clothes anymore because he has outgrown them. His old clothes will not fit his full-grown body anymore so he is forced to wear properly sized replacement clothing. His old clothes became obsolete and new clothes became his standard.
Maturity also means leaving beginner things or basic things behind. When we were in primary school, we learned the basic arithmetic operations like addition and subtraction. We understood that, 1 + 1 = 2. As we grew and moved on, we learned more complex things, yet we did not consider those basic things obsolete. Those basic things became fundamentals. They have become foundational to more complex and more advanced things on top of them. We left them behind, not because they were obsoleted, but because they are very well understood and are so simple to us now, that we can even teach them to anybody who is following our footsteps.
In our spiritual journey, we also need to understand how maturity is defined. Christians have varied opinions about maturity and many may not be able to define spiritual maturity in simplistic terms. We also need to understand what things have become obsolete that are outgrown, and what things have become basic and elementary so that we can leave them behind and grow toward higher perspectives.
What is spiritual maturity then?
What are the things that are rendered obsolete?