You have added some copy-paste content to your website before. But, over time you have understood that was wrong and you removed those old articles and added SEO-friendly genuine content.
Before, you were getting indexed much sooner when you add content. But after removing the old content and adding new genuine articles, you have observed a significant drop in your indexing rate. Despite of adding the site map over Google Search Console, there is still no change. So, after the new additions and changes, can you request a re-evaluation for the website?
Your website may have been caught by the Google algorithms due to copied material or SEO works and may have been penalized for it. If you have such a penalty, you will get a warning message via Google Search Console. By making the necessary changes in the light of the information provided in this message, you can make a re-evaluation request for your website.
If you did not get such a warning, firstly you need to remove the 404 error pages for the sub links that belong to the old articles that you have removed. You can resolve this issue by making a 301 redirection from the old pages to the new pages.
Depending on the bot visits to your websites, your articles will be updated in the shortest time possible and will be indexed faster than before. If your articles have not been indexed even after waiting for a while, you can make them indexed faster by making use of the Fetch as Google.
Depending on the content entry to your website, the visitation frequency of the Google bots will increase and your articles will be indexed much faster.