The basic tenets of "faith" of buddhism are literally
1. nothing is permanent (not even gods)
2. there is no soul (literally "atma" which can also mean god)
3. because humans don't accept 1 and 2, we are unsatisfied
The three marks are the bedrock of buddhism.
Now, buddhisTS, meaning people who call themselves buddhists often do believe in gods or god. Just like here in Sweden most people who call themselves Christians don't believe in the Trinity, the virgin birth, the divinity of Jesus, or any other of things many christians would think are mandatory for the faith.
You need to keep your terms separate. Buddhism is agnostic, it says that if there are gods then they also are subject to the natural laws. Buddhists can believe anything.
Anyone who claims its athiest is mistaken and hasn't done enough research into it.
Can't speak on real shintoism, I don't know anything about it, but the meiji era state-shintoism held the emperor as their deity.