A character trained in a skills in some RPG generally gets better at that skill as they grow in level and experience. Someone who can walk a tightrope at 1st level might continue developing that talent until at 20th level they run up walls of glass or balance on clouds.
Social skills are supposed to follow the same progression. 3rd Edition D&D presented this as the advancement from smoothing over unfriendliness and perhaps prompting the occasional favor, to at high levels being able to bring gods and kings from open warfare to friendly relations in a matter of minutes. This was considered OP for some reason, social-oriented characters dismissed as a viable option. Many games since have repeated this framework, not recognizing the mistake in this scaling.
Certainly the fact that it scales so quickly seems excessive, but it wouldn’t be out of place in a superhero game (and neither would running on clouds, reading minds through the nuances of body language, or many other options available to high level 3.5e characters). The more subtle and pervasive issue I identify is that social skills scaled quadratically - they both grow more potent with level, and the character also becomes a more legitimate authority. A low level 3.5e character has the same odds of persuading the High King as of persuading the local Baron, or a peasant, but is prevented from abusing that because he has limited access to important individuals and is not taken credibly by them (even if he’s persuasive, they don’t know or trust him).
We might imagine that a high level character would be even more persuasive, and thus able to charm his way into an audience with the High King despite lacking lands and titles. We could also imagine a parallel system, in which the high level character is no more persuasive than the low level one, but has far greater access to those important individuals because he is one himself (and will be taken credibly and have some respect for it). Perhaps the former was the intent behind 3.5e, but the reality of how it was played, and of how most similar games seem to treat social interaction, is that a high level character gains both of the above benefits. With this linked increase in both the scope of interactions and the degree of effectiveness, he goes from being able to persuade individuals of little influence of small things, to be able to persuade individuals of great influence of great things; a more balanced framework for gameplay would instead scale up to persuading individuals of little influence of great things, and individuals of relatively great influence of smaller things.
The general fix applied is to scale the difficulty of persuasion with the target (defense-based social combat games tend to do this well). In a game where levels correlate directly to in-world power and import (e.g. old-school D&D), this could be easily simulated by modifying interactions based on the relative levels of the participants. A 1st level adventurer who approaches the duke will not even be granted an audience in all likelihood, and if he was he’d be dismissed trivially, but he’d have fair odds were he meeting with the local baron. That same duke wouldn’t dare reject a request to meet with a 9th level adventurer, and would treat him as an equal; the baron would offer his humble services however he might be of aid. I’m currently testing such a framework, and it has so far proved both simple and elegant in creating sensible outcomes. Equals treat each other as equals, inferiors act carefully before their lords, and the great can impose on those beneath them. Being skilled in Diplomacy or other social skills can smooth those constraints, but the essence of the interaction is still principally determined by relative positioning.