redirect performance

You could use the debugging to just show the URL so that you don’t count in the loading time of the new page. For a random post that is: https://giocone.com/?redirect_to=random&rutpdebug=2

To get reliable information about the duration, you probably have to run it quite often and calculate an average. If another plugin slows down this process, there should be a difference, depending on whether that plugin is enabled or disabled.

You could also look at the code. The plugin Redirect URL to Post is really minimalist. It doesn’t even load anything like images, style sheets and so on. I assume that at star rating plugin needs to do thousands of things to show and save the ratings, to check that everyone can vote only once, for the settings pages and much more.

But you will be in a difficult position to argue with them. Maybe you can disable some of their features, use different caching, a CDN or something like that.

I have no experience with adsense, but I assume that it is basically JavaScript that loads after the page has been rendered by WordPress.

You could check in the developer tools of your browser how fast the resources of the page load. Maybe you find something. It might take more time until the page is complete.

This plugin here doesn’t load anything into pages.