WRC started it's slipper slope in the early 2000's, and it's never recovered, consistently taking steps back and now it's a sad state of a sport, which is a great shame.
I think what made rallying so good was the wide range of competition we had, the unpredictability, and how dramatic the cars used to ride. They still look great, but the sport has lost its way.
I used to love WRC when i was a kid. Now its just all sort of "dried up"
This, the competition between the manufacturers/teams and strength of the drivers is what made rallying so special in the 90's and earlier (Was quite good in early 2000's but that's when it started to die out) Loeb took advantage of the weak competition and a dying sport, sure he was talented but his easy titles where due to the very poor state of WRC competition and it's downward slope. Loeb and Citroen just took advantage of the problems WRC faced, which it never recovered from.
Loeb & Citroen winning everything probably dried the sport up a lot, Personally i didnt have a problem with it because i love Loeb & i thought it was special that i was watching the best driver ever taking on the stages and it was still awesome to see everyone doing the stages as well. When Loeb leaves interest will be restored.
Please read above, the domination of Loeb and his team did not kill WRC, it was due to the competition in general leaving and being so weak (economy and other major factors also) Loeb leaving won't be a magic fix as WRC has many problems to fix and may never return to it's best days.