No doubt there's overlapping complexity in web technologies (e.g. flexbox and grid), partly because we can't re-invent everything from scratch. Multiple players

No doubt there's overlapping complexity in web technologies (e.g. flexbox and grid), partly because we can't re-invent everything from scratch. Multiple players probably also play big role here, single-vendor technologies are easier to get right. But, often the problems are also non-trivial. The web platform is really diversed, there are user-agents everywhere from mobile phone to smart tv and everything between, with extremely varying input methods (touch, mouse, etc), resolutions, pixel densities, performance, etc. Some of the devices are never updated, running a decade old browser. I don't think any other technology faces similar challenges. Actually it's amazing that things work as good as they do.