The Marauders (mainly Sirius and James) were some of the most talented and gifted wizards of their generation. The way they successfully created the Marauders Map and became animagi at young ages (without any help at all) is a testament to their magical talents (except Peter who needed help from James and Sirius). To do some of the things that the Marauders were able to do, one needed to be really good in transfiguration, potions, and charms.
Becoming an animagus is NOT easy, it is a very hard and complex step where making even the smallest of mistakes was enough to cause permanent half-human, half-animal mutations. And creating the Marauders Map was also not easy and it involved the use of the Homonculus charm, a very powerful and advanced form of magic.
If they can be capable of inventing a really powerfully advanced map as well as becoming animagi without any help, do you think that the Marauders (had they lived longer) would have also been capable of one day inventing the very first cure for lycanthropy?
