I wouldn't rely on Unity if I really target for the web. Whenever you hit problems about WebGL or Canvas, it's much easier to resolve with Phaser or another HTML5 framework. Web is hard in itself, thanks to modern browsers with different engines.
In my last workplace we had restrictions for each project like: not having more than 2MB build(which loads projects pretty fast). We were making bitmaptexts, sprite compression and custom builds with Phaser which you'd have kilobytes of projects. Of course, you'd do some of them with Unity too, but not reliable and you are not controlling it mos