Can’t argue that the room is the weak point. Investment should be made here as one of the first steps for any serious audio system IMO.
Yet, we can only get the room so good. But that is not the topic of this thread. Much out there already about this.
The recording/mastering process remains the primary determinant of/limitation to sound quality. Study the stages of signal degradation (starting with the microphone) that our media suffers prior to even being presented for reproduction.
Is your point that we should just throw in the towel on component improvement since perfection will never be achieved re: room/speakers? Many current and past speakers are plenty good enough to hear differences in SQ of sources and amplification.
As for "inaudible gains", I feel sure we would all like to read of your real-life personal experiences that support this rather than only unsubstantiated opinion.
Dave