13. Some poor first year probably got crushed to death by the moving stairs.
14. People can teleport and become invisible at a moments notice. Based off the fact that people have mental illnesses, there was probably a problem with wizards/witches stalking people and I imagine there were lots of serial killers (besides the Death Eaters.)
15. That their world is dying.
Think about it. All of the great magicians are dead and ancient. Time Turners? Nobody knows how to make those anymore. A powerful magic whose methods have been lost to time. The Deathly Hallows, three items that turn well known laws of even magical physics on their heads, cannot be recreated using modern means. The three brothers were probably intelligent and powerful to create them, yet modern wizards find the idea so outlandish they consider them a fairy tale. There are even old magics, like the The Arch in the ministry, that nobody even knows what they are anymore. What purpose they may have served.
The pure blood lines are crumbling, falling back on old money and old blood to prop up their nobility. The segregation and racism deepen the gulfs and serve only to ensure that their world sinks deeper into disrepair. Wars flicker off and on, magic guarded jealously, and even among magical people there are those born without the spark. Squibs.
Certainly there are powerful wizards. Dumbledore was put forward as an example of such. But bear in mind that he also used the Elder Wand and still was no match for Voldemort. The creator of the Sorcerer’s Stone, Nicolas Flamel, opted to let the secret of its creation die with him. And maybe it’s that mentality of wizards, to jealously guard their secrets, that have led to a world that is slowly dying around them.
In addition they are stagnant. They don’t know how to grow. As a society they don’t know how to advance. For the most obvious example let’s look at Snape and Potions.
Snape was a school child, around Harry’s age, yet he was a prodigy. He made vast and sweeping improvements to the art of potions and tried his hand at inventing spells. He was a remarkable young person who was revolutionizing the way that Potions are made and the methods used. He was improving on methods that could have conceivably been in place for hundred of years.
Fast forward all those years. Snape is now Potions Master at the top school in the world. He has political clout and is close with Dumbledore. It has been decades since he was a child and he has likely turned the art of Potion Making into something unrecognizable from what it was only a short few decades previous. Surely the children are learning the Snape Method right?
The children are still learning the same old methods from the same old textbooks. And Snape is forced to teach those same old inferior methods because that’s the way it’s done.