Are you arguing that idealism is a predictive dead-end? I don't think it is any more of a predictive dead-end than materialism is.
Scientific theories are conceptual frameworks which can be used to predict future observations. As such, they make no claims about the ultimate ontological status of their theoretical constructs. Materialists propose that those theoretical constructs (or at least some subset of them) are ontologically fundamental, and minds/qualia/etc must be ontologically derivative. Idealists propose that minds/qualia are ontologically fundamental, and those theoretical constructs are ontologically derivative. Neither is science, although both are philosophical interpretations of science – I see no reason why science (correctly interpreted) should be taken as preferring one to the other.
The part of my qualia which can be reduced consistent, predictive patterns (and, for convenience, a set of concepts which represent patterns, an explanatory models for patterns, within that.)
The idea that there is anything that meaningfully exists outside of my qualia, is the lowest-level of those models, and that that includes other entities which have qualia of their own, is a high-level model (or maybe, more accurately, a conjecture) built on top of those models which might have consequences for, say, my preferences for how I would like the universe to develop, but interesting lacks predictive consequences – its a dead-end within the composite model.
On a fundamental level, outside of any beliefs about the “reality” of the patterns or explanatory models of the “material universe”, objective questions are ones which have consequences on the expectations within that set of patterns, whereas subjective ones are those which do not.