The Board may be a good thing, it may be a bad thing, ane plaintiffs have an agenda (100%). But the court is not supposed to rule on that at all, or what is right and wrong. It’s supposed to rule on the law.
If the NLRB they’re operating a parallel court system outside of the regular court system, where they’re both a prosecutor outside normal Executive Branch oversight, and a judge outside the Judicial Branch, that’s exactly the sort of thing a Supreme Court full of (establishment) conservatives is going to strike down, not because they hate labor (though it might also be true) but because it violates the power structures prescribed by the Constitution, and their philosophy is that these should actually be upheld. The legislature doesn’t just get to set that sort of a thing up to be independent of the other two branches, any more than they get to have a general police power; it’s a usurpation.