My TomTom is ONLY a method for the PC to communicate with the TomTom in order to download updates or to buy new maps, and to add your own content.
It doesn't have the same "marketplace" of extras from other users that we were used to in Home.
You can certainly blame TomTom for that omission but not 'MyTomTom' specifically as it was never designed to do that. TT had plans to create something similar, for the NAV3 models, but I wouldn't hold your breath.
However, you an still add all the things you used to, so long as you have them on your PC or can find them elsewhere on the web.
Taking your list one by one:
Speed cameras:... If you have a TomTom with 'LIVE' capability and a current subscription to the LIVE Services, ,then you will get speed cameras offered to you.
Several other companies do their own speed camera databases which are often better than TT's version. Try a Google search for them.
POIs: There are several good POI libraries on line, with thousands of general or special interest POI sets. Again, Google is your friend
"Demo in 500%" - I'm assuming you mean you want to be able to adjust the speed ofthe built-in demo feature. Sorry, that's just not possible on the new NAV3 models.
Sound Effects - Again, these are fairly easy to find on the web
Computer voices - You've never been able to download those, even with Home
If you need help finding any of the available content, then ask here and someone can probably help (or do a forum search as lists of POI libraries etc. have often been posted up here.