What the Court said was:

Our consideration is limited to the present circumstances, for the problem of equal protection in election processes generally presents many complexities.

Bush v. Gore, 531 U.S. 98, 109 (2000)

the case can be cited, though that may not be the strongest tactic.
See: Lemons v Bradbury, 538 F.3d 1098 (9th Cir. 2008)

Anyway, while there are certainly Supreme Court opinions that are no longer good law or opinions so narrow as to have little precedent beyond the case at hand, I don't know of another opinion where the Court has so strongly discouraged future reliance.

In lower courts, "unpublished opinions" are fairly common. (I put that in quotes because the cases are generally available somewhere). Such opinions are not binding precedent.

Hi, you might find better luck at r/asklaw

There are likely quite a few cases that cannot be cited as precedent, NOT because the opinion explicitly states that but rather because the ruling of the court was not agreed to be a majority of the court. You can win the case by having a majority of the justices (usually 5 is the majority) however, not all of those judges may agree on the opinion of why that party wins. So the opinion could be agreed to be 4 judges and maybe two other judges agree with that that party should win but not on the same reasoning. In such case that opinion is a plurality opinion and it decides the case but cannot really be used because the reasoning is not a majority.

Consider Dennis v US (1951) the vote was 6-2 but the opinion was ageed to by only 4 justices with two others agreeing that Dennis won but not on the reasoning of the other four. Since all cases are different, in reality, then this case has almost not ability to be cited cause you really have to use the reasoning and if a majority does not agree on the reasons then its useless as opinion.

It happens quite a bit I'll try to find another one.