When 勉强 means “contrived, unnatural, artificial”, it is similar to 做作. In such circumstances, 勉强 actions as an adjective. When something is said as 勉强, it is so unnatural that it has a false quality and makes people feel embarrassed and disgusted.
For example,
她唱得还可以，就是演得太做作/勉强。
Her singing is all right, but her acting is overdone.
这件事情他处理得太勉强了，不会有人满意的。
He handled that problem in such an unnatural way. No one is gonna get satisfied with it.
这类寓言似乎太过勉强而不具有启发性。
Such parables may seem too contrived to be illuminating. © economist.com