There was an article on the BBC about the need for people to repair electric vehicles. The main point seemed to be that the high voltage was dangerous and the repairers needed to be licenced.
The interviewee said that there was 600-800V DC in the cars. Undoubtably dangerous, but did garage staff need a licence in exposives to service petrol powered vehicles?
There used to be many accidents. Even as late as the 1960s airliners were being destroyed by fires breaking out while being refuelled by
trained ground crew. It took a long time to determine the cause and introduce new equipment and training that resolved the issue.
Batteries in electric cars are still a new, imperfectly understood technology. There are examples of that for electric cars, and many more for other equipment - just look at youtube.
I have never seen inside an electric vehicle, are they that dangerous or is just common sense needed?
Common sense isn't common. Doubly so in this case, since it is difficult for somebody to have common sense about something they've never encountered before.
The Dunning-Kruger effect is strong

Reading about the Tesla cars it looks to me that repair is a module swap operation, hopefully the on board computing power can tell you exactly what needs changing? So why not DIY? Or are we at the point where not having the relevant pass words means it won't work afterwards?
Where are you going to get another module from? Look at the fires on youtube to see what happens when replacing their laptop batteries with ebay clones.
Replacing a cell in a battery is very different to replacing the battery. That must be controlled for the forseeable future, to ensure safety.