We make judgements on things in a split second and make erroneous predictions on things every minute. That's how the human brain has evolved to function. It might be nice to think that you're immune to these biases but the reality is if he'd scored a goal, you'd be pointing to it as evidence that he's settling in quick. We know that because you've done it before and because you're prone to the same biases, in this case confirmation bias. You're holding back on expressing those snap judgements because a) there's nothing to support your previous views yet and b) it's socially desirable to present yourself as reasoned, calculated and objective.
The funny thing is in this case, there's no confirmation bias on my side as I wanted us to sign Morata, think he's a better option for us than Lukaku and expect him to be a success. I just opened the discussion because it's possible he might not be, and the reality is he struggled in his cameo today. That doesn't mean he'll be a failure but we shouldn't hold back on commenting on it. Particularly not when people are employing bully tactics when others express opinions that are different from theirs.