From a 2018 Washington Post article

>The ratio is staggering. According to the Supreme Court Database, since 2000 a unanimous decision has been more likely than any other result — averaging 36 percent of all decisions. Even when the court did not reach a unanimous judgment, the justices often secured overwhelming majorities, with 7-to-2 or 8-to-1 judgments making up about 15 percent of decisions. The 5-to-4 decisions, by comparison, occurred in 19 percent of cases.

You've fallen prey to media outrage mongering. If you go look at decisions for yourself instead just the ones the media tells you about, you'll find that it is also common for the "conservative" and "liberal" justices to switch sides.

Most cases which come to the supreme court aren't particularly partisan. The purpose of the Supreme Court is to clarify what the law is, and many ambiguities do not fall along a conservative-liberal axis. Someone can be a conservative and still agree with liberals on many things, and vice versa; indeed that's how intelligent people with well developed opinions ought to behave. Even on partisan issues, there is still typically an element of degree - an extreme conservative may see something as reasonable while a moderate conservative may not. That conservative and liberal justices in some cases vote with each other is in absolutely no way evidence that they are not conservative or liberal.

This is true, but it's still much rarer for cases to be genuinely mixed. If you do see a 6-3 decision, it's nearly certain to be along party/ideological lines.

It's remarkable that this was a 5-4 decision against the conservative justices. The vast majority of 5-4 decisions will be a single conservative justice siding with the liberal justices.

When a case is nonpartisan, they will have a lot of unanimity, and a small number of dissents from it. But when the case is partisan -- and a fair number of them are -- they will fall along partisan lines. There just aren't that many cases of serious but non-partisan disagreement.