He's a career 14% shooter.
Last year he shot 17.1
This season he's shooting 14.3 and on pace for 22g, which would tie his career high in 09-10 when he shot 19% (now that I would have called a fluke). However he's now had 2 seasons above his career average, suggesting that his top end is higher. He's done it multiple seasons now. No longer qualifies as a fluke to me.
The significant stat I see is that Brouwer isn't getting the shots he was getting last season and yes, that's IMO, on the loss of Ribeiro (not getting as many quality setups) AND on increased defensive coverage. The NHL knows he can score from that slot area now and I believe are taking his shot away more. Last season he had 111 shots in 47 games (2.36/game), this season he's got 126 in 68 games (1.85/game). That same pace would have only given him 87 shots on goal last year. If he has that shots on goal pace THIS season, he would be around 28 goals at year end at his career average 14% shooting.
I'm clearly not saying Ribeiro is a better player than those you listed, however sometimes chemistry just makes players play better together and I think that was the case with that duo last season.