For a game of skill, ditch skill systems
Ye olde TL;DR - Games with skill systems stunt player growth, while skill-less systems more richly reward ingenuity.
Skill systems are a common, distinguishing feature in modern-style sword and sorcery tabletop RPGs. In the typical skill system, characters receive additional roll modifiers, on top of what their raw ability scores would grant them, when executing certain tasks. The skills which receive these modifiers depend on what the class allows, and what players choose. This construction is meant to represent specialized training that characters well-versed in an adventuring vocation would naturally enjoy.
Conversely, skill systems are prominently absent in Original Dungeons & Dragons (1974) and old-school games cast in its mold. In OD&D’s rules as written, characters aren’t even allowed to make checks influenced by their raw ability. Instead, characters just have x-in-6 chances of success that vary only by the character’s species. Some OSR systems choose to permit raw ability checks, leveraging character natural ability, but without skill bonuses.
The lack of a skill mechanic in vintage and retro games is not an oversight. Quite the opposite, it is a deliberate design choice meant to induce a specific player experience, and mindset.
Time and patience adds up to something
The rationale for devising the skill modifier mechanic is actually reasonable enough, though. It is meant to compensate for a character’s capability of performing feats that their players are incapable of. If your character were limited purely to what the player playing them could do in real life, RPGs would be practically pointless, and definitely unenjoyable. To address this, a modifier is granted to abstract the character’s competency in an area in which they would logically have one.
This idea is so intuitive that it is the basis of the combat (or “to-hit”) modifier, which few RPG hobbyists take issue with. A character living in a time when swords and the necessity of wielding them were omnipresent would know what to do with one. In the absence of this abstraction, players would be on the pointy end of a one-sided bloodbath.
A plus to character skill, a minus to player skill
Counterintuitively, the benefit of abstraction in combat does not hold for skills. Under this model, there is nothing--no consideration of the actual application of skill--beyond the modifier. Following a skill-enabled modern system strictly, no matter how methodically a player describes an action, their character can never do better than their skill modifier allows.
By contrast, in old-school and OSR systems, if a player describes a course of action in enough detail, any character can succeed regardless of ability. That doesn’t mean they always do, but they can.
In this way, skill systems rob players of the chance to refine their play, to increase their real-world skill at the game. Why? Because players simply don’t have to think as critically or inquisitively about the game world under a skill system.
Skill modifiers will keep inching up as long as they level their characters up. And since most games with skill systems level up characters mainly through combat, and combat tends to be strictly scaled to always favor the players, this incremental progress is assured.
Skill modifiers, then, increase via player victory in skirmishes skewed (on the average) to their advantage, and not via employing the skill itself. Players don’t have to make any gains in their understanding of a skill for their character to get better at a skill. As a consequence, the player moves through the game, one premised on creative collective problem-solving, but has nothing to show for it outside of mere entertainment.
In OSR games, your character “skills” improve if, when, and because your creativity and ingenuity in applying character resources did. This is not a limit but a freedom. Rather than waiting for a higher level to accomplish greater feats, your character can progress as you do. The character is limited only by the player playing them.
For my taste, in a game that leaves players to pursue their own ends, this is as it should be.