If anything's the "new IE", it's Chrome! Dominant market position, >50% of people using it, (arguable?) abuse of a platform monopoly (search this time) to drive popularity. It also supports stuff other browsers don't, so we get sites that only work in Chrome - like we used to get sites that only worked in IE. Yes these are "web standards" now but the effect is similar.
(When did you see a site that only worked in Firefox, or only in Safari?)
It's not a Firefox issue, it's a NoScript issue. Chrome with its market share and propensity to implement its own standards, or Safari with its market share, quirks, and propensity to implement its own standards, make much better candidate IEs.
Firefox is not at all the new IE. Firefox isn't worse at implementing the spec than Chrome they just make different decisions sometimes. People tend to see Chrome behaviour as the default of how things should be, rather than the specs.
This isn't an issue with Firefox, it's a consequence of the NoScript extension blocking unsafe features. The behaviour is likely same/similar with NoScript and Chrome.
Chrome is the new MSIE. In both cases, a dominant position was used to dictate web standards in an unhealthy way. Microsoft did it through strategic neglect. Google is doing it by strategic smothering. Firefox and Safari are the web's last stand against an impending Chrome browser monoculture, against Google endlessly ramming new features down our throats and declaring them "standards".
> against Google endlessly ramming new features down our throats and declaring them "standards".
New features that will be used for their intended purpose maybe 1% of the time and fingerprinting by AdTech the rest of the time. What could possibly go wrong handing the Web over to an advertising company?