The problem with sites like YouTube is if they can’t serve you ads they won’t show you the content - some online proxies actually try to swap out ads for their own (some ISPs used to do this too afaik) as this is what essentially pays for the service (tho doesn’t happen with https sites).
If you need a proxy to connect to services, then you’ll need a proxy service which you configure at your router level (and what you usually have to pay for), or if you need one to use via a browser you could use one of the guides like this: