Is the primary use-case only for configuration secrets?

Would it be suitable for a use-case where we manage (hypothetically) 400~ API keys, secrets, usernames etc for different use-cases. Our main application would need to be able to grab the secrets for APIs which run periodically.

I'm guessing Vault is more suited for this.. and not Doppler?

PS. My very last post on HN last week was about secrets: https://news.ycombinator.com/item?id=24625934