Yeah, Get requests will not be able to pull all websites. In fact, most complex websites simply will not come back correctly from a simple Get. This is for a few reasons: deliberate action from site owners to block scraping, Iframed content, complex nested SPAs, and dynamic HTML content just to name a few. Your Get --> convert to PDF --> Print pattern will probably work for some sites, so it will save you some effort, but you're going to have to use a browser to do the rest.
Consider using Power Automate Desktop for this instead. With Power Automate Desktop, you can store your list of sites in an array (or Spreadsheet, or in Salesforce) and loop through that list one at a time, opening a browser window, copying the url, letting it load, and using the native Browser Print to PDF capability. for hundreds of URLs, it could probably be done with the whole load in a few minutes.
