Help with tanking

I'm coming back to OW after the new patch, at least checking the game to see all the changes and stuff after only playing Rivals for the last year. In MR I'm mainly a tank, and while I'm not an insane player, I can hit GM just fine playing solo.

I thought I'd pick up the tank role in OW too, and played some casual games. I did pretty well, usually dominating the match, so I thought about trying some ranked gaming, since I was doing quite well and felt confident.

It was a pretty bad experience though. Overall I felt like I wasn't effective enough, like my team and I were not mixing well or playing together and like I was exploding all of a sudden in the middle of the fight. It was so different from the casual games.

One game a support said I should protect them if I wanted heals, and then in another game the DPS players blamed me because the widow on the opposing team was dominating the game, but I was getting my ass kicked by a Zarya all game long.

Obviously MR and OW are quite different games, but I'm used to having another tank beside me, so I can either focus on fronting or focus on peeling for the supports, and since I'm always tanking alone in OW, I feel like I should mostly worry about what's in front of me, the other tank, rather than a tracer in the backline, since I'm not keeping up with them in terms of speed and probably won't be able to do much, or a widow so far away I barely see them most of the time.

So my main doubt is, how do I play effectively as a tank in OW? Is it my job to take space, push up, stay at the front of everyone and also having to worry about dive or a widow in a completely far away place in the map? Is it my job to counter their DPS and their tank as a tank? And if I must do all that, how do I do it?