Yes, you can definitely make Wilton fondant taste better.
Ideally, you would add candy oil - like Lorann's - or you can knead in extract. You can also knead in a packet of unsweetened Kool-Aid mix if you want to add color and a big wallop of flavor!
I always have my Wilton students knead flavor into their fondant and I have them use Wilton to start with because it is such a great consistency and is easy to work with. After putting it on a couple of cakes, I then recommend they try making their own (I recommend Marshmallow Fondant and Michele Foster's fondant recipes).
I have tasted several students' flavored fondant and with the right extracts/oils, you can definitely make it taste good.