Why was there no need for fancy buildings?

1 Corinthians 3:16

Life For Today Study Bible Notes

Note 7 at 1 Corinthians 3:16: One of the greatest differences between New Testament believers and Old Testament believers is the fact that New Testament believers are the temple of God. God Himself actually indwells them.

In the Old Testament, the Spirit of God would come upon people and anoint them for service. He even came within Old Testament prophets to inspire them to write the scriptures, but this was temporary. In the New Testament, the Lord indwells people through the new birth, and they become His permanent abode (see note 26 at John 14:16).

During the days of the Old Testament, men built God an elaborate temple in Jerusalem, and God said He would cause His name to dwell there so that people could pray to Him in that place (2 Chronicles 7:12-16). But now, in the days of the New Testament, God does not dwell in a building made by man’s hands. He now lives in the hearts of those who make Jesus their Lord (Romans 10:9).

This is why there is no need for fancy buildings for the New Testament church to meet in.
The building is no longer the temple of God. The believer’s spirit has become the temple of God.
If we had a real revelation of the reality of Christ in us (Colossians 1:27), it would drastically change our attitudes, emotions, and actions.

Note on Colossians 1:27

This verse is saying God wants to give me a supernatural revelation of Christ in me.
 I am saying, “Amen, so be it.”

Andrew Wommack's Living Commentary.