First of all you have to know the number of indexed pages (URLs) is not so important for Google. And the reason it doesn’t matter so much is that Google focuses on relevance and impressions rather than on indexed URLs. Think of this: when an individual searches on Google for a specific query, Google will not provide that individual with all your website pages. But the one or ones that is/are relevant to that query and user. So there are (in most cases) 1-to-1 relationships query-URL displayed. There are also some exceptions, when an individual searches on Google for a specific query, Google might provide him with two or more pages from your website (a 1-to-many relationship – one query, many pages).
When you want your website to rank on Google, you want to cover as many 1-to-1 relationships. Of course, you may want to have as many URLs indexed by Google to reach this objective. But it’s not enough to cover all 1-to-1 relationships (that’s nearly impossible) but to get higher rankings for the most important ones. So, instead of ranking on Google with all your website pages but on low positions, try to rank high on Google with your most important queries-pages, focusing your SEO efforts into this direction.
Ranking on top of Google with your most important pages will bring you more traffic than just being present on Google on low positions with lot of / all your website pages. Of course, you can do all that you can to maximize the number of pages indexed by Google but you should focus on impressions more. See which URLs are actually being shown in the search results (those pages are already indexed and ranking on Google) and ask yourself if those URLs are themselves covering the entire range of search queries that website should be covering.
One tip on this subject: the sitemaps count in Search Console is usually more accurate than the index status report (Googling for site:domain.com to see the number of results). The sitemaps count in Search Console tells you exactly how many URLs that you specified in those sitemaps are indexed. While the index status report may contain other things such as duplicate content or navigation structure on your website, leading to incorrect information.