I lived in Rotterdam years ago and what you said around the five minute mark summed it up for me. After 5:30pm the city centre was deserted. Nothing happened, the place was dead. The locals said Rotterdam was where you went to work and Amsterdam where you went to play. Architecturally, you need to see it on a cold, grey, drizzly day. Anywhere can look pleasant on a bright summer's day. Apart from Kubus and maybe the Erasmus bridge there wasn't that much then that really stood out, but then given Rotterdam's sad history, it's forgiven. I was there to work and spent my weekends elsewhere.