You can find out which apps are adding entries and then make necessary changes. At first, you may use the following command to list out active accessibility services:
adb shell settings get secure enabled_accessibility_services
This will provide you with a return listing of enabled services, in this example format:
com.example.app/com.example.app.AccessibilityService
com.google.android.accessibility/.selecttospeak.SelectToSpeakService
If an application is using the accessibility services to add unwanted items into the context menu, you can disable it through this:
adb shell settings put secure enabled_accessibility_services \
"com.google.android.accessibility/.selecttospeak.SelectToSpeakService"
If you notice some other unneeded application that is adding items in the context menus, then you may restrict their permissions to modify the context menu by disabling an app's ability from running in the background:
adb shell appops set <package_name> RUN_IN_BACKGROUND deny
And for enabling it again:
adb shell appops set <package_name> RUN_IN_BACKGROUND allow
However, If you have rooted your phone, tell me to provide you with more effective and straight forward approaches.