No one said that. See the 4 enumerated reasons from Teshuvos Divrei Yoel for the reasons of that determination.
Also note what the Chofetz Chaim, Rav Yedid ZT”L, Rav Berel Soloveichik ZT”L, the Chazon Ish, and Rav Yosef Chaim Zonenfeld ZT”L (all quoted earlier in the thread) amongst others said. There were those who held that his beliefs made Rav Kook a plain Apikores and it is forbidden to listen to his Torahs altogether; others held that his non-Hashkafic Torahs are OK to use but his Hashkafic opinions are rejected; the Mizrachi held from him completely.