The reason I think it's lazy, is it just looks at the results of a very small sample size and ignores the bigger picture.
The chances he had yesterday at first glance, looked like bad misses - in front of goal, no defenders close, but I think on second and third viewing they weren't indicative of someone being a poor finisher. The first one he is at full stretch and struggles to make decent contact with the ball. The second chance from Mainoo he should have scored, again at first glance, it looks easier to score, but on replay you can see there is a defender on the far post, the goalkeeper is off his line slightly. Playing it low and hard towards the near post looks like the right option, with the goalkeeper going the other way. The defender who clears it isn't on the post, Zirkzee doesn't hit him with the ball, he does well to stick out a leg and stop it.
From what I've seen he strikes the ball well when shooting. He generates decent power, while placing his shots. If you look at his efforts, but ignore the end result, then I like what I see. I know for a lot of people the result is all that matters, and in the longer term I agree. However if you are trying to project what a player is, or what they will be going forward, you need to look beyond goal or no goal. If in 3 years time he is consistently underperforming his xG and missing big chances then obviously how good his technique looks doesn't matter and there is a problem somewhere... but after 3 games, I think you need to look a little closer at the context.
A good example of this was Suarez early on for Liverpool. In his first full season he went through a spell of hitting the post a lot. I remember a pundit using the "scorer of great goals, not a great scorer of goals" cliche and I thought they were dead wrong. Unfortunately I was proven right.