[jeltz]

No, you are confusing different aspects of writing systems. Pictoral scripts are often very divorced from the pictoral meaning. Moving away for pictoral scripts is mostly a question about ease of writing which is why the hieroglyphs survived for monuments but more efficient scripts were used for every day writing. Hieroglyphs, outside some very early versions, could express everything spoken Egyptian could.

Some proto-writing systems (e.g. Australian message sticks), which could not express all ideas, were just very simple dots and lines. Going from being able to express only certain things to the full spoken language and going from complex symbols to simple ones which are easy to write are two different processes. So while we can suspect that a pictoral system is from an early stage of a writing system we cannot say that it is necessarily primitive in ability to express all ideas. Plus it might be, like hieroglyphs, only used for fancy texts for monuments and similar.