No one is a winner if they happen to be playing in average to shit teams. Sometimes great players continually end up playing for teams just can't seem to win enough games.
You're right, but this isn't just a handful of seasons. This is his entire career, and he's done nothing. After nine seasons it looks less like coincidence.
Look at Brett Kenny, once all the other star players retired, he was still a champion, and in a quality team he would of still been a champion, be it that he was a metre or so slower, but in those useless Parra teams, if that was all you had to go by, you could say that he wasn't a winner.
But the point is it wasn't all you had to go by. Just like Taupau, you have to look at Kenny's career as a whole, and his win rate was nearly 57% with four premierships! Taupau's career win rate is under 42% and he's never won a finals match. Kenny had only 4 losing seasons in 14 years while Taupau's only winning season in 9 years was 2017.
Unfortunately for him, Taupau has just played for low quality teams. His efforts can hardly ever be seen as the reason for his teams not making the play offs FFS.
Yeah it's unfortunate, and might only be coincidence, but the fact remains he is unproven as a winner. There are a couple of explanations for why he's only ever been at shit teams, besides coincidence. He could be a negative influence or he just might only sign for clubs willing to pay huge overs, which are generally the most desperate ones.
If he had a winning record, like Kenny, there would be no need to speculate.