I think it's less that it's "impossible" but rather that it's expensive.
Honestly we've in general shoved too much shit into the browser that's not strictly related to just browsing web sites.
And you "have to" support all the layers and layers and layers of added stuff, or you can't "compete".
But, at the same time, the goals of making a good-enough browser that mostly works and isn't completely enshittified and captured by corpo big tech interests is a very worthy project and 100% support what they're doing.