I would say that tera made the coverage on mons less valuable since everything can get around that, what matters now is how strong a mon hits and what side effect the move has (status chance, defenses drops, bypassing subs, an so on.)
Coverage is still valuable because not everything wants to burn Tera just to not die.
Wake is more spammable with what it does, Water and Fire isnt too limited in this metagame and and sun is still popping off. Tera Blast also gives it more coverage to use as well, broadening its usage
I'll admit that its predictable but that doesn't mean Greninja isn't somewhat predictable too.
Wake is slower off sun, and thus loses to offensive threats Greninja does not. I also don't think Wake uses Tera blast ever so that is wholely pointless to mention.
Greninja was always carried by Protean. The nerf hurt Greninja far more than it hurts Cinderace or Meowscarada (because Meow was designed with the nerfed Protean in mind).
And Greninja runs specs which doesn't care about the protean nerf. It's very much viable still.