That ruling not only invalidated the Privacy Shield agreement, but in fact prohibits the transfer of any data to any company affiliated with a US-based company in any way (including subsidiaries or even mere suppliers or customers), which comprises pretty much every company out there - US-based or not - because in today's globalized economy you'd be hard-pressed to find a company that doesn't in some way at least transitively deal with US-based companies.
Technically, the reason for this is the US CLOUD Act (https://en.wikipedia.org/wiki/CLOUD_Act ), which requires US-based companies to hand over any data, regardless of where that data is stored geographically. This also means that the common naïve assumption that you're safe in terms of GDPR as long as your data is stored in EU-based data centres is false as well.
So, when following GDPR and this court ruling to the letter, we'd (as in "everyone") pretty much have to stop trading and doing business altogether. Since that's (hopefully) not going to happen, none of this is enforced, at least not consistently or according to the rule of law (which in a way is even worse because at that point law and law enforcement becomes arbitrary and fines will be imposed based on how eagerly local authorities pursue these matters rather than universal principle).
Now, it can be argued that the EU and GDPR really aren't to blame because it's the US CLOUD Act that created this issue, after all. That CLOUD Act indeed is hugely problematic, to say the least.
However, the problem remains and it's on the EU to negotiate an agreement with the US that allows companies to legally do business in the real world (as opposed to an ideal world according to GDPR) again.