There is nothing wrong with your truck. It's your first one and nobody should be slaggin' you for driving it. Some racers can forget that they started with that (entry level) type of vehicle and comment from where they are now...not what it was like in the begining. Granted...some people can afford to go right for the high-end race level stuff...but it shouldn't matter.
You can still learn a lot with the Rustler. You can take your radio and drop it into a more race-oriented vehicle latter on when you're ready to move up (if you want to).
As far as racing trucks on carpet go...well...there are none. Carpet racing any off road chassis (truck or buggy) will always be a compromise. Trucks ans other off road vehicles have suspensions designed for bumps and jumps. If you want to race on carpet (or asphalt) then you're better off getting a touring car or a pan car (1/12 or 1/10).
As long as there is a class for you to run a truck at your carpet track then run what you have. You can lower the truck as far as it will go, add some stiffer springs and heavier shock oil and go for it! The width of a truck makes it (nearly) impossible to get a body to go over the wheels (like a sedan car) so there is a greater risk of dammage when you snag a board or crash...but that's just the way it is with off-road chassis raced on road.
There's more to racing than having the latest, greatest racing car. As long as you are having fun at the track it does not matter what your running. Don't let anybody try and get you down for doing that.
Have fun and keep on racing!