Not at all, this is a myth. The first 10 races of the season are no less important than the last 10 races of the season. Both have a maximum of 250 points to be dished out. The final 10 races of the season merely seem more important because we perceive them as "championship deciding". Truth is, every race is championship deciding. What happens in Australia will have just as much impact on the WDC as what happens in Brazil.Alonso had mistakes in 2010, but what counts is at what point in the season these mistakes were made. Early in the season mid season is always alright it can always be made up at the end.
For instance, take 2012. You might think that Alonso "lost" the championship in Suzuka. Well, what if Ferrari hadn't kept him out in Canada? He would have got 8 extra points, enough to overhaul Vettel for the WDC.
In 2010, all of those early mistakes by Ferrari and Alonso is the reason to why they were so much on the back foot come to Germany. They lost the WDC in races like Monaco, Silverstone, and Belgium - not in Abu Dhabi.
Every race is equally important for the WDC. Well, not this year with Abu Double, but in previous years it was.