Why only core journals are recommended?
When distributing core journals, you should contribute by yourself, and you must not let others contribute for you. If you want others to help you, you should also ask your tutor to help you vote, or ask some teachers in the institute to help you vote. Because many people want to get a core journal as the basis for their future job search, so they can go to colleges and universities as teachers. If you let others contribute to your core journals, it is possible that your paper data will be copied by others, and you will become a plagiarist. After your paper is not original, you can't publish core journals, and you may miss a promotion or graduation opportunity.
Is the intermediary reliable?
Intermediaries are not very reliable. After all, it is relatively easy to register an intermediary now. As long as you can get a certain amount of funds, you can successfully register, and you can undertake the task after registration. If you give your paper to an unreliable intermediary, the intermediary may sell your paper or sell all the data to others, so your paper will be copied by others. Therefore, if you invest in core journals, you must not entrust an intermediary, but you must invest by yourself. After all, people are separated, and you don't know whether others are reliable or not. If something really goes wrong, you will regret it. Therefore, investing in core journals must be rational, so that there will be no problems.
abstract
It is very difficult to write a scientific research paper, so if something goes wrong halfway, it will make you sad and make you regret it. Therefore, when investing in core journals, you should do it yourself. You can ask your tutor to recommend some people to you, and then send the paper to the editor of the journal.