LG is screwing a lot with the WebOS but...
Forget about Flash. Flash is dying and it's not true that it's present on 90% of Internet Webpages anymore.
Most present Flash nowadays it's in Ads form. And most video players (on the desktop) that still uses flash, have the HTML5 Video option and it's there that we should focus.
If WebOS and his browser alone are slow and painfull to use, now imagine it they allow us to use Flash. The TV would simply crash, because Flash is very angry in CPU and RAM, that's why most mobile phones today doesn't even have Flash installed anymore.