Anderson has been consistently underwhelming in Ashes cricket throughout his entire career
I would have to disagree with that statement GAS.
Anderson has turned in some fine performances in Ashes Tests, particularly in first innings where the game is to be won. And these performances are not restricted to England wickets and the Duke ball.
2009 4 - 55 1st innings @ Lords
2009 5 - 80 1st innings @ Edgbaston
2010/11 4 - 51 1st innings @ Adelaide
2010/11 4 - 44 1st innings @ MCG
2010/11 4 - 66 1st innings @ SCG
2013 5 - 85 1st innings @ Trent Bridge then 5 - 73 in second innings
2013/14 4 - 67 1st innings @ MCG
2015 3-43 1st innings @ Cardiff
2015 6 - 47 1st innings @ Edgbaston
Granted his bowling average against Australia is higher than against other countries but he has a bowling averages of 24.2 at the MCG and sub 30 at the SCG and Adelaide.
It has been several years since Anderson has been at his best and, sadly, is judged on more recent performances. However, to say he "has been consistently underwhelming in Ashes cricket throughout his entire career" is clearly not taking into account the performances given above.