> in "medieval" times people also went to church a lot where someone lectured you from a book,

The idea of church as "someone lecturing you from a book" describes only a few christian denominations, few of which were active/existant in medieval times.

I agree that many churches in the US are "20 minutes singing followed by a 1 hour sermon", which is what you describe, but there are also many denominations where the focus is on the liturgy and the sermon is a side note.

liturgy is basically a spiritual practice you do as a group.

say that week's prayer (from the prayer book)

read the psalm, call-and-response (so the congregation is talking half the time)

say the confession of sins

say the Lords prayer

someone reads 1-2 sections from the bible

a quick sermon

eucharist/communion