Rashi does not say that there is no reward for learning. He says that the main reward is for running to the D'rashah. What he means is that seeing as one does not understand the Shi'ur, one will receive some reward for trying, but not for the actual learning. The reason for this is because unlike Mitzvos, where the main thing is doing the will of Hash-m, the main point in learning Torah is to understand it. Otherwise, nothing at all has been achieved.

Afterwards, I saw that the Yosef Da'as cites more or less the same answer in the name of the Seifer Alei Shur. The Alei Shur cites Chazal who say that someone who recites Torah she'be'al Peh has not fulfilled the Mitzvah of Talmud Torah.

Kol Tuv,

Eliezer Chrysler