Given the current geopolitical landscape, citizenship brings a lot of perks these days and that is only accelerating. Also the fix for the issues of people being taxed without representation is immigration reform to make it easier for people to legally immigrate, not allowing non-citizens to vote. Whether by hook or by crook, we'll have to reform our immigration policies eventually because the declining birth rates of the West make it imperative if we want to maintain a world-leading economy.
Um, being an immigrated legal permanent resident does not give you any representation. The problem of taxation without representation is not that immigration is hard, it's that you are taxed, and you have no representation.
You can be a temporary (think H1s, student visas, etc) resident, a provisional permanent resident (essentially it's what lets you be a resident for the extended period it takes to approve a green card in which your original work permit might expire), or a permanent resident (i.e. a green card), and in all those cases you pay at minimum the same taxes as citizens.
What perks does citizenship bring? You have to do all the paperwork if you want to go anywhere, you have to follow all the rules, and you still have to pay taxes even if you leave the country. Being a citizen or even a legal resident is just a bad deal at this point.
On the other hand, if you just walk across the border, you qualify for all of the benefits, and even now get to vote just like citizens, but there are no obligations at all. You even qualify for free housing, free healthcare, free internet and cellphone service, and free food, just for showing up without papers.
