If you're looking for alternative synth plugins, here are a few options:
You might ask: "Why does Spitfire use Kontakt instead of building their own player for everything?" (Note: Spitfire now has its own player, "Spitfire Player," for newer products like BBC Symphony Orchestra Core/Discover, LABS, and Originals. However, their flagship professional libraries still run on Kontakt). kontakt spitfire