Thanks, this is a difficult issue.

I think there is a way to use Researchgate that comply with the law since "scientists are allowed to upload preprints, and peer-reviewed but unedited manuscripts, online for general access".
I have followed this rule and systematically uploaded pdf version of the word document sent out for review, and accepted for publication. A benefit is that it provides the opportunity to create a pdf version that includes any supplementary material that may accompany the main text, and create a better version of the file edited by the journal.

This way, we (as a community) benefit from the publisher's infrastructure to organise the review process while keeping access to the key material (the text) opened, and allow research to flourish. With time, I suspect following this approach will lead to reducing the subscription prices because the sole added value of the publisher (basically stamp and formatting, and some editing) will be better priced.

Cheers,

Morgan Sangeux