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.

For some technical details, see for example http://bugzil.la/668218

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.