Why can't weather plug-ins change the theme of Samsung s8?

To set the weather widget for your phone, you can:

1. Under the standby desktop, press and hold the blank screen -widget- find widget- press and hold the widget to move to the desktop.

2. Add City: After adding the weather widget, click the weather widget on the homepage, and click "+"on the page that appears to search for the added city. (If it is the first time to use it, you can enter the city name in the input box to search. )