For those not familiar with it, Guild Wars 1 used a five-attribute system, with each profession having its own.
Let’s say you were an Elementalist. Your 4 standard attributes were Fire Magic, Water Magic, Earth Magic, and Air Magic. These were available to primary and secondary Elementalists and each of these lines directly boosted the effectiveness of skills under their line. They also had a 5th unique attribute (as did every profession), called Energy Storage, which raised their energy and boosted skills under the Energy Storage line.
Guild Wars 2 uses a much more generic system of Power, Precision, Ferocity, Condition Damage, Toughness, Vitality, Healing Power, Boon Duration, and a Profession-specific attribute.
What is the philosophical difference between these two systems?
It’s a pretty important one. In Guild Wars 1, your attribute point allocations directly determined how efficient you were not at dealing damage, tanking, or supporting but rather at how your individual skill types functioned. That’s a pretty important distinction, and it is one that has created serious contrast in how group scenarios in the two games work.
Gear choices and builds in Guild Wars 2 are one-dimensional. Adapting one’s build to a game mode is all-too-often more about one’s stats than their utilities. In PvE, for example, Berserker Gear is largely regarded as the only optimal choice (and there are a plethora of reasons for this) because damage is more important than any other factor and there is no advantage to alternate gear forms.
In Guild Wars 1, on the other hand, item nomenclature was irrelevant. An Elementalist could be just as situationally effective on a build that ran Earth Magic as with one that ran Air. Both had their uses as damage dealers and both had their uses as supports. There was no drastic difference in how much damage, support, or durability any given character was capable of unless their choice of skills (and corresponding attributes) made it otherwise.
And that is the main problem here. Guild Wars 2 sought to achieve free-form roles by using an archaic system that is counter-productive to this goal. The first game had already achieved that goal swimmingly, and had done so with a much more innovative, customizable, and simple system.
Guild Wars 1’s system was about doing your role(s) – defined by your skills – the way you wished in your own specific way. The Guild Wars 2 system is all about min-maxing to a role defined by your stats – and the game has suffered for it.