Also the legal benefit of scraping the site without the YouTube API is that you haven't had to accept their terms of service.

There's an Android app called GrayJay that got a C&D from Google, and they told Google to kindly fuck off, because they hadn't used any of Google's APIs. Google had no leg to stand on.

RedLib and Invidious hoster here;

I can confirm they do not use any backend API, however this means eventually they (YouTube and Reddit) kick on automatic rate limiting after a while and I have to switch up my vpn connection on my server. it's annoying, but it works if you know a thing or two about proxies and web scraping (the knowledge from scraping can be cross applied to implementing a suitable proxy config)

that said, RedLib's backend token spoofing works a lot better than the Invidious method (Invidious emulates web traffic via Android mobile devices and gets the videos from Google Videos directly, bypassing YouTube for the heavy lifting).

It's not very slow to scrape a website. Works quite well. Your app would appear like any other browser to the site. The trouble with that is that it breaks easily when they change something on their site. Doesn't even have to be a malicious change.