Defining things as perceptions of them doesn't make any sense.
For instance if an large asteroid hits your house while you are asleep (unconscious & unable to percieve it) you still die.
Gamma rays and bacteria existed before we developped techniques to detect them and make them perceptible. Bacteria don't pop into existence in pus from infections when you look at it through a microscope, nor vanish again when you throw it in the bio-waste bin.
That is what Shrodinger's cat is all about -> pointing out that an observer-based interpretation of quantum theory is flawed because it implies the cat is both alive and dead simultaneously which is non-sensical.
In addition, perception-based definition are subjective which undermines the utility of language for communicating information. If "red" can be subjectively defined then telling someone "this apple is red" does not empart any information to them because they don't know what you mean by "red", you could be red-green colour blind and call both "red".