Is it useful to retain the myoglobin of meat which has collected as a fluid at the bottom of the container?
The quote in the Wikipedia article you link to:


  The released myoglobin is filtered by the kidneys but is toxic to the
  renal tubular epithelium and so may cause acute kidney injury


is myoglobin released due to Rhabdomyolysis, so your own muscles affected by this disease can cause  kidney injury, not the meat (also muscle tissue) you're eating.

Having said that, I haven't found any useful purpose for the liquid that gets separated from frozen meat.  I've tried:


pouring it op top of the meat when cooking
adding it to gravy
using it as stock
...


and it coagulates, doesn't give any good taste so I consider it not very useful, so nowadays, I throw it down the sink when someone gives me a piece of frozen meat to cook. 

Note: Freezing changes the texture and taste of the meat, and it's easy to get fresh meat where I live