I think the browser specs are broken such there will always be pathological cases, and always cases where &#x27;you&#x27;re on the performance rails&#x27;. End users don&#x27;t care.<p>This is no different on any other platform. If you program games directly to OpenGL, for example, you run into all kinds of different bottlenecks, both CPU and GPU. Depending on the pipeline of the various GPUS, and what kinds of hazards they have, there&#x27;s stuff you have to avoid, or branching paths you have to handle to get good performance. If you use SQL databases, not all databases can handle all queries optimally.<p>I think it is asking too much of browsers to give them such a huge surface area spec as HTML and CSS, and then ask for them to optimize everything so there&#x27;s no slow paths.<p>The practical reality is, there&#x27;s always a subset of specs known to be fast and well supported and developers just need to know what that is.