I don't think anyone is saying Sigurdsson is the sole reason we're crap - what I'm contesting at any rate is the excuses being made for him personally being poor. Similar to Lukaku ("at a big club with better players he'd shine" etc. etc.) he has excuses made for him instead of acknowledging the obvious - and that is he wouldn't get anywhere near a top six starting eleven.
Is he a good enough squad player for Everton right now? Well, sure. But that's not exactly praise is it - given we're awful and he cost £45m (and yes, that does matter).
That's my issue with the likes of Sigurdsson and, indeed, Lukaku - it's short sighted to think they're good enough for us challenging 8th-12th in the Premier League. My ambition, whilst not deluded, is still far greater than that.