But for me the difference is: in traditional RPG you invest in a skill, as you progress the game you will need to continue to invest in that skill (be it combat,stealth,persuade,pickpocket,lockpick...) because the difficulty curve keeps going up so you will not be able to be effective (level 1 lockpick vs level 10 lockpick) this typically leads that you need to neglect other skills if the "currency"-xp,points per level or per action...- is not given like candy.If I take that from wikipedia (which maybe wrong). It seem to correspond quite well.
For example, there is a door which is locked and I don't have the skill to open it. Well, it up to me to find a way to open it, go around it or find another way to enter (steal the key, kill a dude, convice someone to open it, find a "free pass" somewhere, find another door not locked or a low level one which don't require any skill...). Lot of quests (not alls, indeed) let to players a real liberty on what and how to do. Knowing that generally the quest simply point out the final objective.
In my last playthrough, an optional objective was to reduce the defenses of the enemies before the attack (put poison in the food and burn the arrows). With my character, no way to do it discreetly... I had good armor and good weapons (but not good combat skills...), so I decided to kill everyone patiently one by one (luring them ouside the camp) and complete the objective after, in the empty camp.
Edit : I don't think the fact that a skill blocks a specific path is a problem, because precisely it pushes you to find an alternative path, whatever it is. If you could open the door regardless of your skill, what's the point of racking your brains trying to find another way. Like in Prey with Hacking or Repair "skills" which lock you some paths, but it forces you to find others
On the other hand, if picking a skill opens new pathways but doesn't enforce you to keep them constantly upgraded thats different. Of course, you might find paths closed if you didn't invest on that skill but new skills open new pathways and is up to the player to use them as they see fit (i.e
you can switch between a stealth assasin or a melee brawler practically on the fly at any point once you get the relevant skills).