REST GET without caching
You want to read the Cacheability documentation. it says render arrays, but it also applies to response objects.

ResourceResponse implements CacheableResponseInterface, which has the addCacheableDependency method.

If in any way possible, you want to avoid disabling the cache (which you would do by setting the cache max age to 0), but add the necessary cache contexts and cache tags.

In your cache, that means all you need to do is $response->addCacheableDependency($account).

You also don't need getAccount(), just use currentUser() directly, it's a proxy.