everything is determined by stats
Who chooses these stats? Slot machine?
Yeah but that captures the difference well. There are two types of agency in rpgs: at the character creation level, and during the progression of the story. There can be a game in which there are multiple options to build your characters, but every build is completely railroaded throughout the story and gameplay; and there are games where your build is predetermined, but you do get to choose different story paths and diverge during play - within that predetermined build.
I'd rather be forced into, say, playing a mage, and then be able to make a variety of meaningful decisions with my mage powers, than to be given a choice between warrior/rogue/mage, and then be able to only do that one class-specific thing the devs accounted for in encounters later on. This design philosophy switches the attention of the devs - in ideal world you could have the best of both approaches combined - so in that PoE example a warrior build could choose between different, exclusionary ways of using his prowess - this would probably be the case if you could only make a warrior - but given the variety of builds the reality of the situation is that devs settle for each distinct build having only one way to show its skills or uniqueness.
This is shit because it means that in terms of choice and consequence, the game is extremely frontloaded. The encounters are designed in the following way: you find an obstacle on your way. if you picked warrior, you get to idk, move the rocks due to your high strength. If you picked ranger, you get to find a way around the obstacle. It all references that choice you've made at the beginning, whereas ideally, you should be given multiple ways of using the skills of your chosen class, so that you can make some decisions throughout the whole duration of the game. So as a ranger you could use tracking skills to find a way around the obstacle, but you could also, say, use communicate with animals, to discover a hidden path, and so on.
If I have to pick between the two, I always prefer to be able to play one predetermined role to the fullest, with variety of expressions, than to have 5 or more linear paths to choose between.