You are really underestimating the complexity of the task of building a web engine.
Another problem is that Chrome is already ubiquitous and most of the web sites are simply ignoring the Gecko and only optimise against Chromium.
Don’t get me wrong, I truly wish we had more completion and I hope those projects take off and with time become a viable alternative of Chromium but I am somehow doubtful.
War crimes for thee but not me