This is a source of disappointment for them, and they feel bad that all their hard work has come to nothing. However, they would not have been disappointed if they had done their research, and come to know about the track record of the journal. Then they would have realised that the journal they had sent their work to indeed did have a strong track record of rejection. They would have had many more options under their belt. They would have made sure that they kept more journals as a backup and sent it to them for publication.
Researchers should not only investigate what the rejection rates of journals are, but also what the reasons for those rejections are. It could just be that the journal has been getting plenty of sub-standard material that they had no option but to reject. They also need to look at what types of articles get accepted. Then this will help them plan their work better when they are putting their research down on paper.
Maybe there is a specific format that they need to follow, or they need to look at what type of research gets accepted in the journal, or it could even be that they need to market their work better. If a journal has very high rejection rates then maybe it could be a good idea not to send it to them, but get it published somewhere else.
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