Lack of change is expected. The drawing symbol system is simple. Changing it will be complicated.
For a short time, PTC exposed the underlying layers system that drives how symbol groups work. It made it much more obvious. You could edit definition on a symbol and then open the layers menu and see what layers existed in the symbols.
What I hoped for for a long time was intelligent symbols, such that the sizes and contents of symbols would be managed with relations and parameters. And by contents, I mean e.g. weld symbols would have if-then statements rather than groups, not simply echoing back external values. With the present system of layer driven groups, complex symbols often require repeating the same graphical elements multiple times because of mutual exclusion settings.
It would be an intelligent overlay with Sketcher used to generate symbols. The geometry solver with local section relations to control geometry generation and logic on top to control display of particular elements.
I also hoped that symbols extents would get dealt with as well. Make a symbol that takes little space in one group and a lot of space in another. In order to window-select an instance of the little-space group one needs to select an area encompassing the lot-of-space group, even though the on-screen image is mostly blank. In notes, symbols are given far too much space, acting as if they are a full character. Embedding a flag note symbol into a note column causes the line the symbol is on to have a disctracting amount of space.
