Well the car has been inferior to the dominant Red Bull most of the time. I also think the level of competition in terms of the drivers has gone up. Vettel has got his act together and is proving himself to be the real deal after being quite error prone in the previous 2 years. Hamilton of course is also a fierce competitor, plus Jenson is always improving.
I think your first point is a crucial one, but I also think that Gilles's initial post hints to how strategy has damaged Alonso's chances more than once, which I think we can all agree to (see Abu Dhabi 2010).
Gilles, the issue is that a driver on his own can only do so much in terms of strategy. It is the pitwall that has all the relevant information and the final word on what to do - for example, we could hear Alonso questioning the strategy during the last race, so obviously he was not making the decision there. But you are right in saying that Alonso perceives his input on strategy as one of his strong points. At the time Alonso signed with McLaren it was said that one of the factors for his move was his less-than-ideal relationship with Pat Symonds, with whom he often disagreed in terms of strategy; and Alonso has often said that while it is not true that he asked for #1 status at McLaren, it is true that he asked to have more weight when it came to designing his own strategy, which Dennis refused to give. So it is important for him to participate in it, and that explains why he asks for so much information during the race (as Andrea Stella says in the video link provided a few posts above) and expects his opinion to be taken into account.
Now, I think that in terms of extracting value from the strategy, Alonso has done more than win one race in the last year and a half - otherwise he would not have been 2nd in 2010 and currently running 3rd
From the top of my head, one could argue that he would have had a shot at winning both Monaco and Spa this year thanks to strategy, but that in both cases Vettel was saved by a timely SC; and Monaco last year was another example of how to play the game. Are those examples as spectacular as what he achieved in Japan 2008, where he correctly read the fuel/tyre impact in lap times? No, but one cannot always hit the jackpot!
Fnally, a word on Button, who was brought up by GB: Button is renowed for being very good at strategy in changing conditions. I don't think that Button is better than others at reading the weather, and therefore one must conclude that in some instances he has been lucky that mother nature liked his tyre choices
. But he is very good at calculating which risks he can take, given his easy handling of all tyres, and at being very patient - and as proved in Spa, that takes him further than just profiting of changing weather conditions. He and Alonso are very similar on that.