It’s a bit hit and miss. Sometimes tracking functions are baked into the same JS files that are required for a functional site. You could absolutely do a deep dive into minified or even obfuscated JS code, but many people prefer to use something simple instead where no tinkering is required.

Unfortunately, since the API change, Reddit blocks VPNs even on old Reddit.

EDIT: If you must visit reddit via VPN, consider using sh.reddit.com. It only supports the new layout though.

Because privacy frontends send only the required data without the whole tracking garbage to the corresponding platform. That doesn’t end at API calls, they are missing JS trackers that track your mouse movement, how long you look at a page, etc as well.

Often, a nice side effect is that ads are removed as well.

NewPipe developers are aware of the problem and are working on a fix.

In the case of Tubular (a NewPipe fork), the issue is getting code 403 (Forbidden), which prevents playing the video. It occurred sporadically while playing videos for some time but could always be fixed with a restart. Now this occurs at the very start while trying to play a video for all people at the same time. I’m strongly suspecting that this is a move aimed specifically at 3rd party players.