It's not 2008 anymore. Get with the times.
Let's take FireFoxOS as an example. I have a ZTE Open, the lowest of the low-end, running FXOS 1.2 -- an older, slower, version of the OS. The only advantage is its excellent support for web standards.
There are some awful examples of HTML5 apps on the platform, notably the popular solitaire game offered through the marketplace. There are also exceptional apps, that you'd think were native if they were running on any other platform, such as fast-paced 3d games and physics-based games that run without slow-downs or stuttering at a high frame-rate. Seeing what's possible, there's no excuse for far less demanding apps to perform so poorly.
Now, you do take a performance hit when you use tools like PhoneGap that purport to abstract away differences between platforms -- doubly so when you add-on ridiculous libraries like jQueryUI, which are known to slow-down your UI dramatically. Don't be stupid, don't use awful third-party libraries, and avoid unnecessary layers of abstraction and you can have a fast and responsive HTML5 app.