Starting with yum-2.9.7- 3 exclude option in repo files is ignored. Supplying exclude on command line is still working. In man yum.conf there is comment that exclude is space separated list. Previously it was comma separated list. Anyway, I tested with space, also with only one package. The result is the same - listed packages are not ignored in update list.
*** This bug has been marked as a duplicate of 208520 ***