It was considered a failure at the time by the park / Merlin because it didn't create the expected uplift in visitors in its opening season. Never mind that it was Olympic year, the weather wasn't consistent, there were mistakes in the marketing, that the preceding seasons had been poor and dissuaded returns and many other things which influenced the gate. Never mind also that it had one of the highest rider approval ratings recorded, showing once people were on it they loved it so word would likely spread and people would be likely to return . The reaction, in terms of gate figure, wasn't instant so it will always be thought of as a failure, and this why we ended up with the crappy backwards seats to give them a gimmick to push and why the unique selling point is now held in higher regard than producing anything good.
Just shows what a short term mindset things are operated with, and why there is virtually nil investment on anything other than something new and major (ie marketable) rather than general improvements, which are so desperately required and would deliver long term results. It's all such a shame.