I understand your frustration, we are on the same boat. Xojo2020 Web 2.0 is a new version with many changes.
They changed the way the overall application looks like by using Bootstrap themes. Easy styling for individual controls is not present right now.
There are several threads about styling and several Xojo users are trying to easy the conversion of Web 1.0 Styles to make them work with Web 2.0, because there is the need to have those in Xojo2020. You can visit Web - Xojo Programming Forum to read more about that.
For now, the overall look of your web application can be changed by dropping a new bootstrap.min.css to your application. You can find several free themes on the internet. One site that has a few is: https://bootswatch.com/
If you want to change individual controls, you need to use code to do that, that’s why I posted the link to the docs. If you want to change the Background on any of those controls (WebCheckBox, WebTextField, WebButton) you will need to use code in the Opening event:
Me.Style.BackgroundColor = Color.Blue
You can visit https://documentation.xojo.com/api/user_interface/web/webstyle.html for more information. One important Method is Value, you can use CSS Style Properties, here is a list: HTML DOM Style object
Take a look at the work presented here:
https://forum.xojo.com/t/web2-0-external-libraries-and-helpers-example-project-nash/
https://forum.xojo.com/t/i-try-to-bring-some-of-the-webstyle-functionalities-from-web-1-to-web-2-0-heres-my-project/
https://forum.xojo.com/t/how-to-use-google-fonts-for-web-2-0/
somethings can be a little complex for some users, definitely more complex than what Web 1.0 offered with WebStyles.
I still hope that Xojo can add some easy CSS Style creation and CSS Class option to a future Xojo Web 2.0 release.