I don't think the framers contemplated transgender rights claims when writing the constitution. Or anything about an obligation to provide access to toilets.
So it's probably the most sensible thing for SCOTUS to say this isn't our issue to resolve.
It's certainly an awkward issue and I think architects are already designing unisex toilets in new and redesigned public buildings to offer an extra option. So there's a gradual, accommodative evolution that's already underway. But I don't think SCOTUS should be defining rigid, rights-framed answers at this point. All that would engender is endless lawsuits and ridiculous awards.
As a general rule, I hope liberals will often judiciously opt to leave room for freedom to do its thing, rather than so often to attempt to force issues through the courts.