LosslessCut works great if the keyframes of the video are not too far apart and if you already know where you want to cut. I posted something similar (a web app for automatic silence removal) a few months ago in Show HN: https://www.savvycut.com.
We also use keyframe based cutting for lossless cuts and a smart-cut mode that only re-encodes parts around keyframes (at least for h264 and vp8 codecs). I see that you also experiment with a similar smart-cut feature: https://github.com/mifi/lossless-cut/issues/126.
That seems to work quite well if you re-encode with the same parameters as the original but I guess there are a lot of edge cases.
And I wondered why we suddenly moved to the first page on google for some queries for our app that we posted on Show HN some time ago that competes with kapwing in a small niche (SavvyCut: https://news.ycombinator.com/item?id=28950702). It seems that someone made some room for us.
I guess if you rely on googles monopoly to run your business you should not be surprised if they can remove you at will.
For us, a lot traffic originates from competing search engines that show us on their first page even without creating any SEO spam.
We also use keyframe based cutting for lossless cuts and a smart-cut mode that only re-encodes parts around keyframes (at least for h264 and vp8 codecs). I see that you also experiment with a similar smart-cut feature: https://github.com/mifi/lossless-cut/issues/126. That seems to work quite well if you re-encode with the same parameters as the original but I guess there are a lot of edge cases.