A limp way for the original franchise to finish.
Its predecessor, 'Conquest of the Planet of the Apes', was a weak entry too but remained watchable, though 'Battle for the Planet of the Apes' kinda straddles the other side as it's uninteresting. I didn't dislike it and it is very short at around 82 minutes, which helps. Roddy McDowall is the pick of the cast, though even his performance feels weary at this point.
A 'strong' 6/10 rating from me, if such a thing exists. It was the right time for them to end this (very good, all in all) series.