The reason Wuyi wanted slower progress was, as his cultivation grew, Wuyi understood how important the cultivation techniques were. He also understood that he could use the current method to reach the Qi Master level, but after reaching Qi Master, he could not use the same technique. If he used the current technique after reaching Qi Master, the highest level of cultivation he would reach in this life would be Qi Lord, but after that, his foundation would not allow him to reach a higher level. Wuyi wanted to become immortal, to be freed from any and every shackle this world might have, and for that, he would need to find a better method to cultivate.