No I'm probably a guy that think Shiro is a crazy talented guy, but not the best rookie.
In terms of impact on the overall game B1t is better in my opinion, but they play very different roles so it's a bad comparison.
Imo Shiro came into a team that already had a well and good structure, and they could have done very well with another awper that can hit shots aswell.
Same with Vitality, they had done well with another good awper, like device or something for impact.
But in Na'vi they were a team that missed exactly one piece, a really good 3rd rifler. B1t came in and filled that role, which I would argue no one else could have filled in as good of a way. And after he joined all pieces came together for Na'vi and they won the major which had eluded s1mple for so many years. B1t enabled his team and was the missing link, I've never seen another rookie have such impact and therefore I think B1t has done the best rookie year ever.