From my point of view it's exactly not a partial solution, with the UK (and perhaps Germany) sharing data with the US if I e.g. use an UK SaaS email provider. It doesn't make any difference to EU citizens.
It's a partial solution, not in the sense that it improves anything by itself, but in the sense that combined with getting other countries to stop sharing data with the US, it would prevent Europeans from being spied on by the US.