If you can't easily delete or export my data, it means that you don't have a coherent, legible record of exactly how my data is being processed. You can't be sure if my data has been leaked or stolen. You can't guarantee that you'll be able to notify me in the event of a breach. You can't prove that my data was lawfully collected. I can't check the data you hold on me to ensure that it is accurate.

The GDPR is easy to comply with if your data protection policies and processes were decent to begin with. If you have read the text of the GDPR and can't see how you could bring your business into compliance, then you are almost certainly doing something seriously negligent or seriously shady.