Should I persist with article that keeps getting rejected?
It depends. That is my answer.
If you really believe that your paper offers an interesting contribution, then:

Try to improve your manuscript by doing this:

Extend and update the state of the art (maybe adding those related papers you mentioned in your question).
Be honest, be thorough, be critical: What are the weak parts of your manuscript? (Are the introduction, the theoretical aspects, the conclusions... bad written? Is your contribution not clearly highlighted and/or explained? Could you add some numerical examples to your manuscript (if this applies)?) Identify them, and go and try to improve them.
Try to add an explanatory chart of the process/method/solution you are describing or proposing. (Relevant) drawings can help people to understand your article and can make it more appealing to referees.
Get your manuscript reviewed by a colleague you trust. This is a must-do. Maybe you are not seeing something that is obvious to other people.
Of course, double-check the language usage. Ask some expert to review grammar, vocabulary, etc., if necessary.


Maybe the problem is not with your paper. Try to look for the right scientific journal. Some hints:

Look for articles related to your research topic in the Web of Knowledge (WoK, https://webofknowledge.com/) or Google Scholar (GS, https://scholar.google.com/) and see in which journal they were published (for instance, you can use some keywords related with your paper).
Similar to the previous one: If you are interested in sending your manuscript to a certain journal, look for articles related with your manuscript that have been published in that journal (using advanced search in WoK or GS). If you don't find any match, probably it is not the right journal.



If you already tried all the above suggestions and they did not work, then consider to publish your research as a technical report before quitting, at least.
EDIT:
I also recommend you to read these two articles:

https://www.elsevier.com/connect/8-reasons-i-rejected-your-article
https://www.elsevier.com/connect/8-reasons-i-accepted-your-article