If we all end up living inside one 'super app' like Claude, are we still able to access all our other tools and data?

Yes. The idea is that even though Claude (or a similar assistant) becomes the primary interface, MCP connections let you still access everything you normally would through other applications without leaving Claude. However, this depends on the quality of each company's MCP implementation. Legacy companies (the example given was Intuit) may have MCPs that are not yet clean or fully featured, so it is on those companies to improve them. When an MCP is first released, it may start generic and get updated over time as real use cases emerge — described as an ongoing project to keep improving based on how people actually use it.