The phrase "are too subtle to" is correct and usable in written English.
It can be used when discussing something that is not easily perceived or understood due to its delicate or understated nature.
Example: "The nuances in her argument are too subtle to grasp without careful consideration."
Alternatives: "are too faint to" or "are too delicate to".
Cashews, while nice, are too subtle to stand out here.
The differences between the autistic brain and the normal brain are too subtle to be seen with the naked eye but with the aid of the software, scientists were able to identify five parameters where differences could be detected.
Since our brains are hypersensitive to color and signal but rather dumb when it comes to tiny time changes the illusion is convincing, but the differences that produce it are too subtle to notice.
The 28percentt response rate is traded for the 31percentt response rate; differences in effectiveness that are too subtle to be noticed by an individual practitioner justify ongoing refinements in therapy.
Barro's response: More-recent swings in spending are too subtle to produce a statistically significant pattern.
The experimentally observed small variations are too subtle to be explained or predicted by the used modeling methods.
Loomis nonetheless was too subtle to jump to sensational conclusions.
The temptation, as always, is to decode, but Cunningham's work is too subtle to yield to linear solutions.
As Time Goes By by Derek Taylor Though Taylor started as a journalist, his unique wit was too subtle to work in cold print.
But, as the example of Henry VIII makes clear, the difference between divorce and annulment is too subtle to survive much contact with reality.
Using a highly sensitive type of magnetic resonance imaging, researchers studied 63 servicemen wounded by explosions in Iraq or Afghanistan and found evidence of brain injuries in some that were too subtle to be detected by standard scans.
