Not sure what you're exactly asking for. Google/Youtube does provide an "official" API for youtube searches:

https://developers.google.com/youtube/data/reference/rest/v3...

It's rate-limited but other hacks to scrape Youtube without the API will also be rate-limited as well unless you try to trick Google via unapproved hostile methods such as commanding an army of residential ip zombies and aggregate it.

Fundamentally, the index of Youtube videos lives in Google's servers so you're beholden to Google to get results from it. If the issue is that the Google's official results from search queries are not surfacing the videos you think are actually there, it means you'd have to build a duplicate (massive) "shadow" index to return those missing videos. To build such a beast, you're back to hitting the brick wall of rate-limits again.

   copy(
     'yt-dlp ' +
     [...document.querySelectorAll('ytd-video-renderer a#video-title')]
       .map(a => {
         const u = new URL(a.href);
         return `"https://www.youtube.com/watch?v=${u.searchParams.get('v')}"`;
       })
       .join(' ')
   )

It's intended to be used as a youtube-to-podcast-player tool, but seems like it fits your use, too.

Since youtube api won't help with this someone needs to build a video index and a good search algorithm on top. Would be nice to be able to search through indexed subtitles too.

That's kinda the nature of YouTube downloaders/scrapers including yt-dlp. It's not exactly a public API that YouTube's offering to support.