Is the word "interest" well applied here?

[Arly]

Hi, I have this sentence:

X is a technique whose central interest is improving modularity.

Do you think interest is well applied here? I think not, since improving modularity is more of a concern of X...
However, I can't use concern (due to already using it too many times). Can you give me a synonym? Or interest is correct?

Regards.

[Kitosdad]

X is a technique whose central intent/purpose/goal, is in improving modularity.
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Keep it simple ... Keep it interesting.

[Arly]

Thanks. Purpose will do. Also, is "whose" correct? Shouldn't it be "which"?