Yes, those are very real problems but they are also very rare. All of the people affected in the video are pretty much the only people affected (there may be around 20 - 50 other people who have had the same or similar defects but in the grand scheme of things, that isn't much).
It is true that there are some defects with the left joycon (however it doesn't affect everyone) and yes, the dock can scratch your screen. If you're that worried about scratching your screen though, you should buy a screen protector. There is also an issue with the joycon straps getting stuck but that shouldn't be a problem unless you're blind or don't pay attention to little symbols that tell you how to put the strap on.
Yes, these problems can affect you, but don't let that deter you from getting a Switch. These problems are very rare.