"I think transcending ethnocentrism ultimately must involve discarding our legalisms about "who is a Jew"? And we can't do that without a schism from the Orthodox. Our Jewishness will no longer be reliable to them. We really will end up like a new group of Samaritans, people who identify as Jewish but who traditionalists regard as irretrievably polluted, no longer authentically Jewish."

This schism you advocate for has already happened. Orthodox Jews I have met won't date or marry Reform Jews because they feel they cannot be sure the person is really, Halachically Jewish (aside from differences in lifestyle, but say, in teh case of a ba'al tshuva...). Even more so with non-Orthodox converts.

Moreover, I learned recently at a shi'ur that I went to on Shavu'ot that even if people are born Jewish if they stray from religious observance they are legally considered to be like non-Jews and are treated as such, including that they can't touch kosher, non-mevushal ("pasteurized") wine lest the wine become treif, you can't eat their food or off their dishes, etc. Non-religious Jews are treated esentially as non-Jews as per relatively recent Halachic decisions.

So there, you have your wish.

But I think a sense of Jewish peoplehood is a good thing and worth keeping, in my opinion.

Why?

Because WHEN YOU LIVE AS PART OF THE JEWISH COMMUNITY then it's like a place "where everybody knows your name...and they're always glad you came." And that place can be anywhere in teh world where latge numbers of Jews congregate. I have seen people run into old friends from school and camp that they haven't seen in 10 and 15 years on teh Upper West Side or at parties run by Jewish organizations. It imparts a sense of belonging that most people today are sorely lacking, with teh result being all the alienation and despair that we see in modern life. Sure people may get in each other's face and people may get sick of being amongst the some people all the time, BUT as long as people don't cut themselves off like the Haredim and keep porous boundaries, you can have a nice cozy community life and feeling of belonging that is increasingly rare these days.

Why throw this away? Is being "like everyone else" worth it, really? I don't think so.