If you choose to implement it badly, then yes it can damage the compressor wheel. Solution, dont implement it badly.
There are also many pictures of people using pre-compressor with no damage, and so far my own has sustained no damage. Although Ive only been using it like that for a few months.

And of course experience is better than google. Ive been using water injection for 20 years. It's simple and it works ! There is nothing difficult about a internal injection setup. There are a wealth of setups around these days, from simple to complex, or you can opt for an ecu controlled system.
It is far far more effective than any external setup will ever be, and hence offers far more potential. IMO the only time an external setup will be of real benefit, is if the intercooler is already poor.
Solution there is to use a better intercooler !

As for it being difficult to implement an internal injection setup, that's just nonsense. it could never be easier these days because there are so many ready to use kits. As for water running out ? If you're that incapable of checking or spotting a low level warning, that's entirely your own problem.
Really, all of the problems you are claiming exist, could only exist in your mind if you've never actually used water injection and you spend too much time thinking about things.
It water runs out or fails to spray, damage will only occur if you choose to let it occur. There are many ways to make it 100% safe

If you choose to build any system badly or poorly, then it will carry bigger risks. the same applies to absolutely any aspect of a modified car. So the simple solution is to do the job properly and the risks will be minimised..