There are many changes within iPadOS15 - of which one is the loss of the Today view on the first Home Screen.
Whilst you are now able to freely position widgets on any of the Home Screens, you have lost the “compact” first Home Screen layout (that previously shows a compressed 5x6 grid of App/Folder icons and the Today view). Now, without the compressed view, Widgets individually occupy elements of the 4x6 icon grid - and will displace some App/Folder icons as necessary.
The net effect of adding Widgets to the Home Screen(s) results in reduced efficiency in using available screen space on Home Screens.
Apple do invite constructive feedback, comments and feature requests via their product feedback pages. For iPad and iPadOS:
Feedback - iPad - Apple
You are encouraged to make use of this facility in expressing any views concerning issues, bugs, or functionality changes of which you are unhappy.