if you see google is not more indexing your website pages then first thing you need to check is you are not blocking google bot from indexing using noindex meta tag or you are accidentally blocking your website or google bot if you are using cnd or from your server end.
Perform Live URL Inspection in Search Console
First thing you need to do is fetch url or perform live url inspection of your website url and check the url status and if you see any error then fix the error in search console.
Hit By Google Core Update
If you are noticing issue after google released core update then your website is hit by google core updates and you need to optmize your website as per google spam policies and follow guidelines and start recovering your website and start debugging your website pages by comparing traffic from previous months and find reason for the drop and try to find pattern and optimize website and this mainly happens with content and quality issues.
Technical or Server Issue
If your website is having any technical issue or 5xx server level errors then google bot will fall back when trying to crawl your website and you need to check with server logs of your website and try to fix any server related errors.
You can also check the crawl errors in search console crawl setting and find out what difficulties google bot encountered when crwaling your webpage and server or dns error issues.
Don’t Block Google Bot
If you have blocked google bot from server side, CDN level side (accidentally) then you need to unblock, or with noindex, robots etc and see.
Website is NEW
If your website is new and wondering why google bot is not indexing then you need to wait for some time and provide useful and helpful information on your website and often for new websites it takes time to show websites in google search and there is no guaranteed time here to show in google search. But for most new websites, it doesn’t take much time.