Am I missing something with Winston's Tesla Cannon?

Winston excels in mobility and getting out of a bad fight easily. He also excels in what I like to call "personal combat arena".

What I mean is, through the use of his easy mobility to get to the other team's backlines, especially where Widows will usually lurk, he can hop in, plop a shield down, creating a mini space where he can fight the enemy without fear of getting chipped from other team members of the enemy. His mobility also lets him do a lot of work going against Mercys who are flying around to other team members, making taking down the medic a lot easier.

That is why Widowmaker's 2nd counter, besides another Widow, is a winston, because although his weapon is a very slow DoT, Winston has a huge HP pool, can shield up to create a personal area to fight in, and can easily jump back out should his HP get too low, then jump back whenever ready.

The advantage of the Tesla Cannon is its wide cone of fire, which makes it able to easily hit agile targets like Tracer and mechless D.Va, as well as hitting multiple enemies if they're all in the cone. This is particularly handy when entering a Symmetra turret nest, as a quick sweep will destroy all of them immediately.

The DPS is definitely on the low side, but it's usually enough against frail characters that Winston loves to jump on, like Widowmaker or Mercy. Winston's strength comes from his high health, shield to isolate himself from the majority of the enemy team while behind their lines, and booster jump to drop on a target and keep chasing while dealing constant damage.

Try Doing a melee every few seconds while firing, it does a couple of things.

1. Conserves ammo so you don't have to reload as quickly

2. Gives an extra amount of damage along with your cannon

XQC, who is known as the tank god recommends this tip in his Winston tips video.