Sketch is great, but it's Mac-only with absolutely zero intention[0] of supporting anything else.
I'm a Mac user and have a Sketch licence, and use it often for personal things, but if you're looking to build a piece of software that supports workflows with multiple people working on / implementing designs independently in a professional setting, expecting every company using your software to enforce a fully Mac-only office* is only going to get you so far.
* I also work in a pretty-much-Mac-only office, so I do acknowledge that this strategy is not entirely fruitless, it's just not going to replace Fireworks.
I'm a Mac user and have a Sketch licence, and use it often for personal things, but if you're looking to build a piece of software that supports workflows with multiple people working on / implementing designs independently in a professional setting, expecting every company using your software to enforce a fully Mac-only office* is only going to get you so far.
[0] https://www.sketchapp.com/support/requirements/other-platfor...
* I also work in a pretty-much-Mac-only office, so I do acknowledge that this strategy is not entirely fruitless, it's just not going to replace Fireworks.