What you describe is not the fault of the GDPR. It is the software providers that want to keep applying things in the old ways (where you give up your personal data). There are many dark patterns at play here. As far as I know the GDPR requires opt-in (the NO option) to be the default, so it is the easiest and should be a no-brainer (no need to go through all configuraiton settings to opt-out).
Also they have specified rules for how a Privacy Policy must be drafted, and thereby removed much of the ugly legalese you’d usually find here. The problem here is that - with easy to understand texts - lawyers can still build in the same loopholes that you just as quickly will overlook.
But I agree GDPR is still far from perfect and has already shown a number of dark sides, like e.g. an important downside is that it favors the big tech companies, who can easily throw enough money in their system to comply with the rules, while for SMB companies this is a struggle (but that will only be a hurdle at the start, as new software will be developed from the ground up to be compliant).
The annoying popups are once again choices of the software creators, and there are automated solutions to get around most of them (consent frameworks, dialog suppressors, tracker blockers, etc.). But better solutions are still maturing. Note that I do not find the popups all that annoying (except if they have dark patterns), because they make me aware of the bad practices of the site.
Too much going off-topic: Yes, GDPR must be further improved, and we need additional laws to get things in order!
Regarding the design of the site, I suppose a simple static page if you must have something on the humanetech domain.
Yes, in the bullet list for the project I was thinking of a single Markdown document - easily edited with any editor and stored on Github, that is automatically transformed to html by the static site generator that creates the community website (Jekyll).
The signature part sounds very technically complicated and I’m sure that means using an existing third party service. I suppose we could jump into writing the Declaration on Github to get started?
Yes, the bullet points are just a possible feature list. Collecting signatories is of secondary importance after creating a good text, and could also be omitted if too complex. But it can reside as a feature request in the Issue tracker of the project.
Note that my awesome-humane-tech list contains a number of example Manifesto projects in the Ethics section from which we may borrow (parts of) this mechanism.
Besides drafting texts, we can draft and launch a first awareness campaign to attract attention to the effort.