D&D General Mike Mearls says control spells are ruining 5th Edition

[EzekielRaiden]

Right. The problem is that this creates the contradiction that more skilled = less skilled as you will fumble much more often due to your much increased skill level. That's why my group came up with a house rule that made fumbles progressively less likely as you leveled until at the highest reaches you could not fumble any longer.

One possibility, if one wishes to pursue this, could be a "fumble confirmation" roll (just as 3e had a "critical confirmation" roll), but instead of being keyed off the target's AC, it's keyed off of the attacker's level in combat-focused classes: your Fumble Threshold is 20-level. So a level 1 Fighter has a 5% chance to save a fumble and turn it into just a hit. A level 20 Fighter has a 100% chance to avoid fumbles.

With this, you gradually mitigate, rather than it happening in sudden leaps and starts.

I strongly dislike fumble rules and so I would never use this myself. But it seems like a pretty nice, straightforward way to represent gradually growing skill, and a small way to reward folks who stubbornly stuck with Fighter (or Barbarian or whatever) all the way to level 20.