Its just another step in his development. He's still at the same level I feel and he'd had these misses last season too. The only difference is that the chances aren't as many because teams are suffocating him of any space or time by doubling up on him. When he comes deep to play in some space, our options upfront end up with the same problem and a lot of it is down to none of the midfielders breaking lines to create space. The only player doing it every single game atleast a couple of times is Matip and every time he successfully does that we create a good chance. We need that to happen from the midfield.
If he is being more heavily marked, which he is, then surely that creates space somewhere else? But as you say, we are giving him the ball in positions that are very difficult for him to play out of, so that he cannot channel the ball into whatever gaps are created.
I agree with both of these, it's a combination of factors. It feels to me like Salah hasn't really had any of the tap-in chances against the top teams this season and that, at times, he's really been feeding off scraps (again, especially against the big teams) but I think there's also a level of adaptation that we can perhaps expect, or at least hope for, from him. As Rouge said, if Mo's very tightly marked then that means someone, somewhere else is free. I think some of Mo's best games this season have been ones where he's dropped a little deeper and created more. I hope/suspect that pre-season will a) give Mo some tools to adapt to this new challenge and b) see the team as a whole spend more time on attacking fluency again - while we have actually scored the same amount as last season, I think it's also clear that the emphasis this pre-season was on defensive shape and a bit more variation to our pressing game. I think that's come at a bit of a cost to our sharpness and decision-making in front of goal, especially on the break.
Another factor to be considered is fatigue. Mo has played almost every minute of every game and, while it's clear that we've been managing workload within games, there's been no mental respite for him. Since a very difficult world-cup he's been under non-stop and immense pressure, and never at any point had an opportunity to take a mental breather, or to sit on the sidelines itching to get onto the pitch.
However, it's also extremely exciting to think that this team has so much more to come - imagine what we could do with a bit more fluency in our attack, and a bit more freshness and competition through having one or two more top-class options to bring into the mix?