I some cases the "people do illegal things regardless" argument can hold some water, but that's not the case for the GDPR, which is worded very clearly and hence it's really obvious that this kind of thing violates it.
Most of these banners violate the GDPR even before they're showing up, because the GDPR actually restricts your ability to embed non-first-party content without consent. That's why Google Fonts violates the GDPR, for example. Arguably every vanilla Wordpress install violates the GDPR because Wordpress embeds something from s.w.org on every page (presumably for install count / analytics reasons).
This kinda sounds like a bad thing but it's not. It's actually a huge boon, because it's an excellent legal excuse to get rid of embedding stuff from 213789 origins and CDNs, which only has negative performance effects since caches have been origin-segregated for years, meaning that even if another page uses the same jQuery version from cdnjs, it will be downloaded again anyway.