Absolutely not. Every user can access all shows on Mixcloud for free. Creators can upload unlimitedly for free. This free experience will not change due to channel subscriptions.
Creator channel subscriptions (formally known as Select) is a subscription layer on top of this experience that allows fans to subscribe to a channel for a small monthly fee to directly support the creator and their shows. Subscribers receive additional features on that channel such as offline listening, upfront tracklists and access to exclusive content.