Developers are ambitious. We want to build better apps now not in 6 years time when the W3C have finally moved on this or that issue. Right now webkit is enabling developers so it wins. Supporting every browser is either economically not viable or not possible without sacrificing features. If mobile firefox wants to compete it needs to step up. If developers are voting with their feet and actually using webkit features in the wild then they are defacto standards. Firefox better pull its finger out or it will die.
In all of the above cases, Firefox actually does support the features used by these sites, and has for a long time (years, in some cases). In most cases the developers would just need to tweak their UA sniffing, or add some -moz properties alongside the -webkit properties in their styles.
Mozilla does need to "step up" -- but work required to fix cases like these is not technical. It's about gaining user marketshare, developer mindshare, and improving the standards process.
It's true, and since everyone upgrades their phones every two years it's not like there's a chance of older versions of a hegemonic browser haunting developers' dreams, right?
