The restrictions on the technique made sense.
This technique couldn't be considered weak by any means. Techniques were meant to work against those of your level, any that could work even a single level above was considered a top tier technique amongst top tier techniques.
Whether this technique was strong or weak wasn't decided by who it could be used against, but rather how effective it was against enemies of the same level, and if Ryu was correct, mastering this technique could practically make something invincible at the same cultivation level. If you had a middling comprehension, you would never be touched. If you had a perfect comprehension, you could even use it to kill in a single strike without your enemy even being capable of reacting.
Such a technique was excellent.
But Ryu had his reasons for his reservations. The fact that a technique of his would suddenly become useless against an enemy that was too high leveled was a huge turn off.