No, the Data Protection Act (2018) is just the legal instrument which sets out the (UK) GDPR. It is 'technically subject to GDPR anymore', it's just a different one (with essentially if not entirely the same contents).
That's not right either.
The GDPR is law because it's an EU Regulation that was made while we were part of the EU, and it became UK law automatically when it was passed, as regulations do.
The Data Protection Act 2018 augments the GDPR, but the GDPR would be the law of the land with or without the DPA.