You’ll find a new way of understanding how hard a ride is, it’s called the toughness score. It’s a formula that first accounts for the time taken to do the ride, then adds up the time spent at each gradient. It takes longer to get up a 10% slope than it does to get down it, so an undulating ride will still score highly if it has some steep or long climbs in it.
Your own perception might vary, but if you know a few of the climbs, have a look and compare. Does it make sense?