If they don't like it here they can leave.
Man, I know you know that's not actually true in practice, unless by leave you mean kill themselves. Relocation, especially on a national scale, is not exactly something you can just do, and for any number of people it's effectively becoming permanently homeless or outright committing suicide. Which is only a choice in a real damn technical sense.
Any case, the argument such as it is for non-citizens appears to be input. Citizens would get the vote cause they're citizens and dicking around with that probably isn't worth the effort. Non-citizens would get the vote if they're meeting the same responsibilities citizens ostensibly have (paying taxes, contributing to the economy, meeting some base level of civic investment, etc.). Basically making the argument that if you're giving money to the state and/or making it a better place, you should be allowed some degree of influence in how said money or effort is used.
Ain't so sure I agree with it, but I can kinda' understand it. Some rando living in another country that happened to be born in the US, that gives pretty much nothing to the country, not even living in it and the knock on effects of that, getting to vote when someone that's technically a non-citizen but been living here for decades (even if they're legal and trying for citizenship, buncha places have thoroughly fucked immigration processes where they could easily be trying for that long and not made it yet), paying taxes, contributing to the economy and so on and so forth, doesn't, is pretty sketchy on the face of it.
There has to be some kind of limit there, yea. If just anyone who expresses the desire to vote, regardless of citizenship status would be allowed to vote, we'd see that come next elections, the US suddenly would turn into a very popular destination for Russian 'tourists' on election day haha.
Most (all?) countries have a system in place for becoming a naturalized citizen. You might argue (and I would tend to agree) that the system in place isn't perfect and could use improvement. But given the example of the US system...
Naturalization Eligibility Requirements
Before an individual applies for naturalization, he or she must meet a few requirements. Depending on the individual’s situation, there are different requirements that may apply. General requirements for naturalization are below.
Be at least 18 years old at the time of filing Form N-400, Application for Naturalization.
Be a permanent resident (have a “Green Card”) for at least 5 years.
Show that you have lived for at least 3 months in the state or USCIS district where you apply.
Demonstrate continuous residence in the United States for at least 5 years immediately preceding the date of filing Form N-400.
Show that you have been physically present in the United States for at least 30 months out of the 5 years immediately preceding the date of filing Form N-400.
Be able to read, write, and speak basic English.
Have a basic understanding of U.S. history and government (civics).
Be a person of good moral character.
Demonstrate an attachment to the principles and ideals of the U.S. Constitution.
There's nothing there that's all that difficult to overcome other than possibly the fairly ambiguous "be of good moral character" which could be used to weed out just about anyone.
In general I don't think 5 years living here and a very basic understanding of the common language and system of government is all that much to ask. Granted, actually getting past that first hurdle to actually live here legally is often the tough step, and I agree that needs to be reformed somehow... but just focusing on the naturalization process on it's own. I don't think that's too much to ask in order to have the right to be a citizen (and vote) in the US. Some other countries make it even easier than that.
As for the "love it or leave it" attitude, I get what you're saying, but at the same time, if your choice is living for a few years in a place where you don't really agree with the politics and can't vote to change it, but have the possibility somewhere down the line of gaining that vote to change it but can otherwise live a relatively safe and possibly happy life or death... yeah... I'll go get myself a pocket phrase book and study for the next 5 years.
Once again, there are MANY things wrong with the system. But citizenship as a requirement for voting isn't one of them. Also Frumple, I get that you're just considering the other side, but that was just the reply that happened to be the most recent in that chain.
EDIT: And while I understand why some people might feel that way as well, it's just a line that you really can't cross.
As a kid I always wondered "Why don't they initiate a test for voting so kids who were knowledgeable enough about the system could have a voice too. I'm a grumpy old man now and while I know why kid me thought that. I also know now that maturity is a thing you just don't understand until you have it. As a child your brain just hasn't fully formed yet, you haven't had experience with a lot of things. And while I risk insulting by calling immigrants childlike... that's not my intention, it's a new place, a new culture. There are experiences that it would be good for them to have, that they could probably get most of in that 5 years of residence. Knowledge that you can only pick up first hand. Experience that might round off some of those sharp edges that get caught on the "way things are." So stated with full acknowledgement of the irony involved, try walking a mile in the moccasins of a citizen before you start coming in and trying to change things.