English Translation
We cannot help admiring their effort.
I think
Usaha mereka patut dipuji.
is more natural in bahasa Indonesia.
According to the University of Leipzig Indonesian Corpus, “patut” (worthy) is used with a passive form of verb such as “dipuji” (praised) and “diapresiasi” (appreciated).
Indonesian also frequently uses a passive form for several reasons. Indonesian is a “main topic first, adjunct follows” language. “We” is not the center of the topic, so starting the sentence with “Usaha” (effort) is more natural.
Also, “usahanya” means “his/her/the” effort, not “their” effort. The “-nya” suffix should be replaced with “usaha mereka”.