The main objection to B/eternalism is that it doesn't explain change, as either reality .or illusion....as the WP article says.

B theory: Let there be this thing called spacetime which encodes all moments of time (past,present, future) and space (i.e., the universe). The phenomenal experience of existence is akin to tracking a very particular slice of spacetime move along at the speed that time inches forward, as observed by me.A theory:

The problem is how the tracking works. If you were allowed some sort of moving cursor, that would easy. But you're not.