A few speedy partial responses off the cuff to this J Street "perspective."
I too support democracy in America which shouldnt be a left-right issue. But the importance of Israel to Jews today and in the future shouldn't be downplayed. And it shouldn't be either/or.
I doubt there's a Jew in America who's not to some degree concerned about what's been going on in America regarding the growth of Antisemitism and the public comments by prominent officials. Sometimes focused on Israel; but when the talk is about various long-time "ultra" Conservatives being "Israel First"
But it's not just "The Threat" comes from the Right and not the Left. It's too easy to disparage or downplay the antisemitism on the left. Shouldn't just want to build alliances with certain groups on the left and not on the right. There are some Red lines. But don't have to agree on every issue.
1) The issue re Israel is never "Criticism of Israel." It's unfair criticism, or unreasonable criticism, or far more than just "criticism" but anti-Israel hatred. Most people can and do distinguish.
2) "the organizations with the largest budgets and loudest megaphones place Israel – not Jewish life in America, not democracy, not civil rights – at the center of their mission."
I don't speak for ADL or Conference of Presidents (or AIPAC or anyone for that matter. I personally would have J Street inside the Conference or if was determined not going to be destructive to the Conference. Americans for Peace Now - now with AMEINU as "New Jewish Narrative." are already in). ADL are very-much "damned if they do; damned if they don't. Attacked from the left. Attacked from the right. Attacked by other Jewish groups on left and right
There are numerous Jewish organizations in America. And Synagogues. Israel is important to most of them. And traditionally, Israel has been a unifying issue for American Jews. (Perhaps not quite now). And Israel actually brought Jews to the Jewish Organizations, as they were otherwise mostly secular. But American Jewish organizations have been in the forefront in the fight for civil rights and against racism and for civil rights. But sometimes those they fought for didn't reciprocate in their fight against Antisemitism and racism. And famously in the later 1960s Jews found themselves the targets of antisemitism - famously in the NY schools...Famously in the Crown Heights Riots etc.
Some of the people you want Jews to be allies with. That's great in theory. Jews should be allies with people across the spectrum. Different organizations are exactly that. It's a little hard to be allies with people who hate you. Or are seeking to demonize, denigrate and ultimately destroy Israel.
You can argue about AIPAC; but I don't find it unreasonable in the slightest that an organization that's central focus is promoting the US-Israel relationship; should be engaged in supporting those politicians who are pro-Israel. (Once AIPAC got officially involved in political campaigns a few years ago; that's reasonable I find. Plenty of other organizations, often with Jews, who are multi-issue - and oppose the same such people on those social issue matters. (The majority of American Jews of course, famously being Liberal and voting Democrat.)
If anything J Street is the "aberration" - not for your social views; but that as an organization set up as an at least- ostensibly pro-Israel organization, focused on Israel; you've expanded to include these other issues to base you contributions and support on.
I think you ignore a number of American Jewish organizations - starting with the Jewish Council for Public Affairs and URJ/RAC, National Council of Jewish Women who are very active on these issues.
I think perhaps less disparaging of Evangelical Christians who have been long-standing supporters of Israel and generally a bulwark against Antisemitism.
And of course there's a limit to what American Jews can do. And can't just pick Liberals over Conservatives. So yes set up new groups. Ask George Soros/Open Society to provide funds to them (rather than to some of these other groups which I could mention.)
And finally as I've said before: I believe J Street could make a major contribution by publicly criticizing those in the Democratic Party and beyond who are truly-denigrating (not just criticizing) Israel. And even denouncing some of those attacks on AIPAC which go beyond the pale.