Braid and The Witness are both mediocre as puzzle games since they rely on inelegant gimmicks to carry weak core puzzle mechanics.

Some of the levels in Braid randomly have different world properties with no consistency or communication to the player.

Braid is also just ugly so I think it's a bad game.

The Witness is better as an adventure game than as a puzzle game since it's so pretty, possibly the most beautiful game ever, although the puzzles are somewhat interesting.

The Witness' primary gimmick is integrated well, but some of the area-based puzzle themes are bad and harm the overall feel of the game.

Still, the rest of the game's aesthetic is executed so flawlessly that it doesn't do enough damage to make the game bad, but the panel puzzles definitely aren't the reason The Witness is good.

It's not necessarily the case that better puzzles could be designed, the theme of drawing a line on a panel is inherently limiting when you want to create hundreds of puzzles.

I'm optimistic about Jonathan Blow's next game based on Sokoban, because the puzzles have a tested mechanical foundation the game is likely to avoid the pitfalls of his other games.

It also seems hard to imagine any bad gimmicks that might be added to a game where you move on a grid.