Balancing Clarity and Efficiency in RPG Ability Scaling

In character abilities leveling design, I’ve always been interested in finding an answer to the question: how to scale percentage-based buffs and debuffs? So that they look clear to the player, but also increase efficiency in a meaningful way.

✏For example:
— If you increase the percentage value, you will get stat inflation, power creep, and a feeling of more hardcore gameplay in the late game.  Or uselessness at the beginning of the game.

— If based on specific fixed values (not the percent ones), it does not work well with targets of different types.

— You can do it like in some MMORPGs, where the strength of the buff/debuff is calculated based on specific parameters of the character. But it’s complicated and also old-fashioned in some ways.

— A talent tree can work well, especially if the buffs/debuffs are given additional mechanics with which they start to work a little differently. But how then can this system be made similar to the leveling of other character abilities (like damage, armor, or HP-related ones)?

Sometimes there is a feeling that it can be done either “great looking” (when it works simply and clearly) or “with a systematic approach” (when it harmonizes well with other systems).