After changing default theme to custom theme contents and blocks missing

By Default magento 2 with sample data with luma themes used Widget to display static content in homepage and all parent category(What's New, Women, men, gear etc..) in luma theme.

In Luma Themes all static block and Top category page called from Widget. 

You can check widget from

Content -> Elements -> Widget

There are list of widget are available here and all widget are assinged to Magento Luma Themes.

So when we create new theme, Based on parent luma theme, All sample data are missing in our new theme because widget are not set in Our custom theme.

If you want to display content same as Luma theme, You have to create new widget same as Luma theme from widget section from admin.

Or

You have to set static block for your category page and homepage content.

So Problem is not your custom theme but default functionality in luma theme takes static content from widget.

Thanks.