~만 못하다 (man mo-ta-da) – (A) is not as (adjective) as (B)
This is quite similar to 보다 더 in that you would use 만 못하다 to do a comparison between two nouns too.
When the first noun (attach subject marker) of the sentence is worse off than the second noun (without any marker), you attach 만 못하다 to the back of the second noun.
Examples: 건강에 좋고 맛있는 음식은 주스가 과일만 못해.
Juices aren’t as good as fruits in terms of health benefits and taste.
In terms of being good for health and taste, juices aren’t as good as fruits.
한국어 능력을 개선은 혼자 책을 읽기가 한국 친구와 같이 언어 교환하기만 못해.
Reading books alone isn’t as good as language exchanging with a Korean friend in terms of Korean proficiency improvement.
In terms of Korean proficiency improvement, reading books alone isn’t as good as language exchanging with a Korean friend.