This line of thinking is said to be contrary to how the game is meant to be played. When the going gets tough, swapping heroes to counter the opposing team’s composition is encouraged. While it’s suggested that this is how the game should be played, the learning process required for each character may requires time and dedication.
It’s a bit like what Bruce Lee once said:
It’s similar to having a main character in fighting games or MOBAs. You’ve become very proficient at that one character and thus can better tackle different situations with that particular set of tools.
Perhaps the compromise here is to be good at one offensive hero, one defensive hero, one tank, and one support. Of course, if the demand is too much maybe playing just one main hero and one support hero will suffice for now.
A big part of the fun in Overwatch is learning how to play each character and trying out different play styles. Perhaps you’ve done that in the past few weeks, and you need a bit of a change.
Maybe trying one character out for each succeeding week can help make your Overwatch experience better.