For the web you can now use Cocos2d-x[1], Godot Engine[2], PixiJS[3], and/or Phaser[4].

[1] https://www.cocos.com/en/cocos2d-x

[2] https://godotengine.org/

[3] https://pixijs.com/

[4] https://phaser.io/

Unity also has a very good pipeline for building webgl targets. You can virtually ignore the platform concern until the very end, as long as you aren't being ridiculous with real time lighting and texture resolution.