Yes, God is much more than a mere physical thing, but we are physical and need tangeble objects in our lives.
As we begin to fill the church, it is a lot like an extended family who is returning home to share in our commonality. We have all become one family through our faith and through the Holy Spirit. These people are no longer strangers, but brothers and sisters in Christ who we are called to get to know, to love, to care for, and to share our lives with.
The sacred altar where the sacrafice and celebration of the Mass is held. This is the holy place where through the mystery of the Eucharist, Jesus is made physically present to us in his glorified state in the species of bread and wine.
St. Francis in the garden.
We were not meant to be alone.
God created man and woman. He created us to partake and share in his life. He created us to be social.
In times of trial, in times of joy, we are to share with each other. That is what family is all about, that is what community is all about.
So what makes a parish church so special?
Answer: All of the above, plus it is a spiritual home for anyone who wants to enter.