Remove access only for subscriber?

The roles and capabitlies is flaky and does not function properly.

The traditional “roles” as you and many others know them, e.g. subscriber, contributor, author, editor, admin, are actually groups of capabilities, so it’s not that capabilities are “flaky” so much as perhaps you chose a capability that isn’t clear-cut enough. I suggest looking at the second-level role of Contributor and choosing a capability that the Subscriber role doesn’t have, such as edit_posts.

Roles and Capabilities

I don’t anticipate adding per-role settings anytime in the near future.