Sketch exists thanks to the genius of Quartz / Core Graphics. It does not have a rendering engine per se and struggles even with path ops [1].
This technical debt may soon be the end of Sketch. Because apart from Adobe, there is now Figma with smart people like Evan Wallace who can really "decide" [2][3].
With C++ core, Figma can go fully native [4], and it's puzzling why they have done this already.
[1] https://twitter.com/vmdanilov/status/892358827378696194
[2] https://www.figma.com/blog/building-a-professional-design-to...
[3] https://medium.com/@evanwallace/easy-scalable-text-rendering...
[4] https://twitter.com/evanwallace/status/673959396104273921