in the very next breath scream about how adding supreme court justices or limiting terms or adding states is absolutely not a thing anyone should ever due because precedent! Norms! The unthinkableness of it all
These are all different issues:
1. New states: Do the people of Puerto Rico want to be a state? If so, they should. There are referendums on this, and on independence, and the usual answer is "keep the status quo," primarily because territories are taxed differently. Anyways, this one is up to the citizens of Puerto Rico, not you or me. Personally, as a mainlander I think eventually they should "shit or get off the pot" and either become a state or declare independence, but most people there seem to prefer keeping things as they are, and until recently there was no political will from elsewhere to change that. DC is trickier since it was set up to be a certain way, and people moved in knowing the rules. My preferred solution would be to keep a small federal district and give most of the residential land back to MD. I would be concerned given the current climate whether free speech rights could be guaranteed to all citizens without federal oversight, so I think the federal government does need control over the mall, the land with the major institutions of government, as well as some nearby military bases. We simply cannot have a long-term Portland type situation, where people worry about being attacked if they peacefully support one political position instead of another, in our nation's capital. If DC becomes a state and the federal and state government are able to sort this out, though, I won't lose sleep over it. (If DC becomes a state though, expect a big push by Republicans to start distributing different agencies across the country.)
2. SCOTUS term limits: Who considers this controversial? Typically, term limits are a right wing populist idea.
3. Court packing: This would be a new level of norm breaking -- not done in almost two hundred years (back when the Republic was just coalescing as a nation). Expect if you do this, that the court will be packed again by the other side later, and so on. (The idea that one party is just going to perpetually have power from now on is ludicrous -- the overreach / pushback cycle is common in American politics, and SCOTUS stacking would seem to me like it would trigger that.) So eventually the Court becomes more like a shadow legislature -- a new House of Lords so to speak. Not sure this is really the outcome you are intending. It's anti-democratic, but honestly democracy is currently on the ropes and authoritarian governments (China, Russia) are rising. So maybe you think democracy is failing and we do need to make our system less democratic and more aristocratic? Seems like an odd move for the progressive left but these are odd times.
4. Gerrymandering: I'm told Republicans do this more, but my blue state is gerrymandered and there have been prominent court cases about this. Gerrymandering is bad. We should all oppose it everywhere. Nobody wins but political insiders.
5. Voter suppression / voter fraud: This one is weird because the norms are so clear but the details are a mess. Voter suppression is bad and every citizen that wants to vote should be able to. (Including former felons but excluding current felons. Also excluding non-citizens.) We should affirmatively encourage getting people to the polls. However, the idea that "there is no voter fraud" is a political one. There's lots of individual examples of it (I know people who have personally done it, unfortunately), but there's really not been many systematic studies of it, and that's constantly touted as "proof" that it doesn't really exist. Sorry, I'm skeptical. Let's go commission an extensive study on this, well funded with non-partisan actors. Let's figure it out. Anyways, note that lots of countries way poorer than us have figured out how to have biometric voter IDs so there is no reason we could not do it here and just be certain everything was done fairly. I would support affirmatively funding programs to make it accessible as possible to obtain a biometric voter ID, and phase it in over time. In fact, you could make it mandatory that people get their biometric voter ID in order to get benefits (food stamps, driver's licenses, etc.) -- that would do a LOT to make sure we got as close to 100% as possible. If you care about democracy, you want to make sure people trust that the elections are fair. Right now, neither side does, and that's problematic.
I know someone is going to link to a Bloomberg article or something explaining exactly how THERE IS NO VOTER FRAUD EVER, HOW COULD YOU POSSIBLY THINK THAT (despite personal experience with it), and to cut it short all I can say is that I really wish that I could trust that it was an accurate reflection of reality and not actually propaganda from partisan media. It might actually be reality. I just can't / don't trust it. I'd need to understand that non-partisan people I actually trust were given time and money and dug into it and concluded that the safeguards in place are sufficient -- what I've read to date sounds a lot to me like "well we haven't really looked but you know see no evil, hear no evil it's OK so any concerns about this at all are just secret voter suppression efforts."