the technical achievement is (quite) nice but yeah,there are many reasons why we see more and more ports/emulations of classic 3d games and still no custom made new game.
just to name three big ones:
-you need 3d artists
-your dev time and with it costs will probably be much higher than for a 2d title
-connected to the previous: its not sure whether there´s actually already a revenue model for flash first person shooters for developers of the games
sure you can go with the rule: create it and they will come (to play it) but yeah,i can imagine lots and lots of people would also play a well done flash first person shooter in the browser but how many clients/other outlets are there for making a propper profit on a 3d first person shooter played in the browser?
As complexity and dev time for a title raises of course expectable returns should raise, too, otherwise its not worth it for a commercially working team and probably too time involving/ difficult for a group doing it just for fun.
Personally i know many outlets who´d buy a 3d first person shooter game if well done but few who´d be into paying way more money for it than for a 2d or fake 3d game which could probably attract a similar count of players.