Typically in every other game a sniper trades off their advantage of being able to instantly delete people from across the map for less health and being weak up close, you know, balance. They excel at long range but are weak up close.
Widowmaker, with 200hp, her assault rifle mode, and grapple to quickly reposition if she gets dived on, was not a balanced sniper, she was a sniper with all the advantages of a frontline DPS.
But now that Widowmaker actually being treated like a sniper and getting a weakness people are complaining?