I get your point, but this would be a to drastic change for a core mechanic, that is tied to so many other things. How do other stat bonuses affect this? How are base values designed? Are there different scalings for the different classes? What is the use of legendaries if stats are freely selectable?Gw2 is a pretty old game and I'd rather not change the way stats work as a base concept.

A different game (like a successor) could definitely try different concepts, like you mentioned. Just like gw2 is different from gw1.

Another thing I like about the current stat system is the simplicity (even though it is complicated by runes). The fixed stat combinations totally remove that part from the theorycrafting and make gearing much easier. Get Berserkers gear and you can play almost every power build. Get Vipers and you play condi. No need to get that specific item from this one boss, that is only used by reapers.

Your system reduces the need to grind gear (can be good), but increases complexity to find optimal stat combinations.