Well, if you are asking this question, then you do not understand what I was talking about.
In order to sue someone, there has to be an actual controversy; federal courts don’t render advisory opinions in the US (see: Art. III, §2, Clause 1 of the Constitution of the United States). To have such a controversy, you have to have someone who has the standing to initiate the complaint (they are actually harmed by the complained of actions of the defendant/respondent), and you have to have an actual controversy that has arisen (“ripeness”), and not yet been completely resolved (“mooted”). If you cannot meet these requirements (case, standing, ripeness, not moot), you cannot sue in federal court.
So in the case in question, the “state” had arguably taken property from the plaintiff by insisting that an easement of access existed to the purported graveyard. But the Constitution of the United States doesn’t preclude takings, just takings that aren’t justly compensated (Amendment V, Constitution of the United States). So when the “taking” occurred, that’s not something that gives rise to a “controversy”, unless it is not justly compensated.
The whole point to the case is that, in the past, after the Williams case, you couldn’t claim to have been unjustly compensated until you’d gone through the entirety of whatever process the “state” in question had for handling the issue. That could mean going before a town council, going through some sort of administrative hearing, going through a state trial court proceeding, and then following all of this through appeals up to and including whatever the highest court of the state was. That’s expensive, and tilted in favor of the “state”. The legal theory is that, until you’ve been through all that, you don’t know for sure you’ve had your property “taken” without “just compensation.”
This case chucks all that into the oubliette. The Supreme Court decided that, as soon as the “taking” occurs, even if you haven’t been through the entire process that could remedy your complaint in state court, a “controversy” has arisen and is ripe for adjudication in federal court if you assert you weren’t justly compensated at that point in time. This means that the federal court system now becomes an alternative venue for private property owners to litigate the issue of just compensation for a taking. And, as the minority in the dissent note, that means there will undoubtedly be an explosion of “takings” cases in federal court.
So, from a legal standpoint, the reason not to allow it was that the Constitution didn’t allow it as being not yet ripe. From a practical standpoint, the reason not to allow it was that it will result in property owners being able to choose the venue in which they wish to litigate: state court or federal court (or, potentially, both), which means that the federal court system will now get a lot more say in exactly what “just compensation” really means.