The People App in Windows 8 used to be a super hub for contacts, different types of telephone numbers, postal and email addresses and other items. It was quite good initially in Windows 10 too but has now become fragmented, does not sync properly, and often fails to record relevant details from Google contacts. It seems to have lost its purpose and is now frustrating to use.
It used to work seamlessly with the Windows 10 Mail and Calendar App on Windows 10 computers tablets and Windows 10 Mobile devices, AND the Outlook Mail and Calendar App on Android and iOS.
It used to be possible to set it up to be the default contact manager on Android, using the Microsoft Account it was linked to as the primary default contact list. (Of course it would work with Cortana too but I understand why that feature has been retired.)
I do not know if my bad experience is due to a change in Android or Lenovo because I have a Motorola phone, but since Android 9 and with Android 10 I am now having real problems keeping my contacts organised. I can no longer use my Microsoft Account contacts as my default list, and had to revert to Google, but often details I change on my phone are no longer carried across to the People App on my Windows 10 computers and tablet.
There seems to be some confusion again between different departments in Microsoft developing features separately without a focus on the user experience - especially for those who do not use Microsoft 365 on their machines. I hope the People App, Mail and Calendar App and other stock apps within Windows 10 will be kept in focus with other developments in Office, Teams, Edge and so on.