I think if you threw someone into Taiji who had never in their life played The Witness or heard of it, they would find it frustrating and boring. Conversely, if you have played The Witness, you'll spend your entire playtime wishing it was a better game.
The difference is where The Witness had very simple rules to all its puzzles, it held both a deceptively hidden secret game under its hood and layered its puzzles together for its more complex puzzles. It's not a spoiler to say that stars work by grouping two together in The Witness. Taiji, on the other hand, is only challenging in that figuring out the esoteric rules of its puzzle symbols is mind numbingly frustrating. Every puzzle type in Taiji has like 2 or 3 different rulesets that can change on a dime and you're just expected to interpret without any explanation. There were entire segments that I completed without knowing entirely how the puzzles actually worked. The entire art museum section is half reasonable and fun puzzles and half nonsense that, even after finding the solution, left me completely dumbfounded.
I think there are a lot more ways to criticize Taiji but worst thing it does is that it gives Johnathan Blow credit by comparison.