McDonalds had received a few hundred complaints out of
10 billion cups of coffee served. The temperature of the coffee was not a problem; it was, and still is, the temperature at which all good coffee shops and restaurants serve coffee,
including McDonalds. If you go get coffee at McDonalds (or Starbucks or pretty much anywhere else) it will be served to you at around 80 deg C, and sometimes even higher. This temperature is recommended by professional coffee associations [1], and it's the temperature at which any decent coffee machines holds your coffee.
It sucks that Stella Liebeck was injured. Nobody deserves that. But she was burned because she squeezed a cup of hot coffee between her legs while she messed with the lid. This is, by any reasonable criteria, an abuse of the product, and protecting a few people from such foolish choices would mean depriving everyone else of decent coffee. Fortunately that hasn't happened yet.
1 - https://www.ncausa.org/About-Coffee/How-to-Brew-Coffee