There are 6-rated players I'd rather have in the team.
Liverpool started with Diaz and Salah, meaning that Darwin will rarely play as a 9 - it will be either Gakpo or Jota, and they will play in a more supportive role - not attacking one.
Darwin will get some rotational minutes - but would be the first player to get kicked out of my team if I had him there.
It is not like he got injured or played as right back, he continued to play exactly what he was playing in last friendly games with similar minutes. I would also argue that maybe Klopp prefers Gakpo for his pressing against stronger teams while Darwin could be more useful to break down smaller teams.
Not the one I would pick, I even rate Joao Pedro as better fantasy asset and he is 5.5 but if I have already chosen Darwin for whatever reason I would give him this game against Bournemouth.