As said hal, barry.. Etc were humans trying to step foot on holly grounds. Wally can now. He is a god. He is one of them. Then again even if we take your notions into account. That was before doomsday clock, where gods were asked for inaction. Now, a indifferent inactive manhattan (a god) is willed into action by the ultimate man of action(superman) .
“I am a being of inaction. On a collision course with a man of action. To this universe of hope… I have become the villain.”
The whole you can't change destiny thing was manhattan's whole shtick.
“We're all puppets, Laurie. I'm just a puppet who can see the strings.”
Even,his actions to change mess with dcu metaverse was because he saw superman punch his lights out. He genuinely believed that was his fate and destiny which cannot be changed. (he might not have even wanted to change)but, that didn't happen. If this is a continuation of that thread from doomsday clock.he has developed and changed. Manhattan has learned to act. If He has chosen his successor in wally, to do the act. Wally has to fight destiny or time or whatever.