A church building, at least a Sacramentally oriented church building like the two I currently serve, may be similar to a museum in the following sense.
1. Beautiful artwork in the form of stained glass, architecture, banners, sculptures, images, etc. And, this artwork is often given in memory of someone. Often, not always, a plaque nearby tells the significance and purpose of the art.
2. Certain items move and change with the seasons. Colors change. Objects change. Depends upon the season. The curator (often the pastor) and associates (altar guild, worship and music committee) see to the changes.
3. Many of the items in the sanctuary and nave are not intended to be touched and handled by everyone. We certainly expect a certain kind of reserved behavior and conversation while in the Church building.
4. Not only is a "no touch" and "no abrupt and unnecessary loud noises" policy in place, but there are certain places that not every may go. The lector is reserved for the reader; the pulpit and altar are reserved for the Pastor and other ministers.
There are probably a few other points that may be made, but you, the discerning reader, need no further illustrations.
The reason a church is not a museum has to do with the people who visit. All of the artwork, colors, architecture serve to assist the people who gather there for special occasions and on Sundays, to worship the God revealed to us in Cross and Resurrection of Christ. The church gathers around the Word (The Holy Scriptures) and the Sacraments (Baptism and Holy Communion). In the midst of the Church is Christ. And in Jesus' name and in the power of the Holy Spirit we offer our praise to our heavenly Father who gives us everything.
The people do not gather to look. The people gather to worship the living God. And, God promises to be present among us.
The difference between a museum and church building? The presence of God and the worshiping community!