Church is a local expression of that universal eternal reality. The church gathered is a visible expression of the invisible eternal reality.
The Bible assumes people ‘in Jesus’ gather together. It’s what people did straight away after they became Christians as we see from Acts 2. They met together daily. Hebrews 10:25 says:- Let us not give up meeting together, as some are in the habit of doing. Also to keep the ‘one another’ commands that are given in the New Testament you must be together.
Bonhoeffer says:- “Christian brotherhood is not an ideal which we must realize; it is rather a reality created by God in Christ in which we may participate”