In original Fallout you had three groups of character data that were grouped by how you change them permanently
- attributes were most static, you can permanently change them only with surgeries
- perks you gained every 3 or 4 of levels
- skills you could increase every level up
This made your decisions about perks and attributes more substantial
This gave you flexibility in start that if you got some new piece of weapon, you could became proficient with it in couple of level ups.
In the start, you would suck with it, if you haven't preallocated points in skill .
But sooner or later you became certain build, specialized in certain skills.
So that system gave good combination of flexibility and choice consequences.
In F4,
everything is a Perk, even attributes.
And you can modify them every level which makes them not that different or special.
Without skillssystem, every weapon you get, you are using it as you were born and raised with it.
Which is fine for shooters, but really dumbs down roleplaying with weapons.
Removing of skills was also needed for that terrible dialogue system.