Mathieu,
I know you and like you personally, that why I can say that this mail is clearly not your best argument.
Despite saying multiple times this is not a manifesto nor against Wikidata, your mail seems clearly fuelled with biases and misjudgements (especially Wikidata can't be « discontinued quietly » not now that it's so widely used in Wikimedia projects, even the wiktionaries are *already* using Wikidata).
Dissecting each single phrase point by point is violent, borderline mean and definitely not constructive ; cross-posting this mail on multiple places doesn't help either. This is not the good way to debate peacefully.
Some of your argument are good but most are quite poor and really missed the big picture.
For better or worse, Wikidata choose CC0 and it will be quite difficult to change the licence now (the example of licence change on OpenStreetMap illustrate it quite painfully). We have to get approval of the community, there was multiple lengthy and non-conclusive discussions, it's not something that will be done with a ranting mail.
For me, the situation is quite simple, Wikidata needs lexiographical data and the Wikimedia projects needs Wikidata to have these data. Nobody suggest in no way to do license laundering nor to violates Wiktionaries licence, in fact we could simply import Public Domain sources (in the same way the wiktionaries did, in frwikt a big chunk of entries come from the
Littré and the
Dictionnaire de l’Académie française, and there is enough dictionaries waiting in the Wikisources to keep us busy for years) but it would be a shame for Wikidata to not profits from wiktionarists expertise.
Let's get over the petty and unsolvable issues and work intelligently and pragmatically to improve Wikidata.
You entitled to disagree with the way that has been chosen and not take part in it (and from your editcount, I see that you don't) but please don't destroy others efforts and try to be more aligned with the wiki-spirit.