The language almost never matters for normal apps. The easier languages come with many available solutions (classes) but since those classes are made as universal as possible they are slower overall.
E.g. Array.Copy spares you a lot of tinkering but if you impelement individual manual strategy like ReadMemory, WriteMemory, CopyMemory and marshalling for every different datatype like integers, strings etc., it will be as fast as pure C. The modern 'easy' languages like Java, C# and VB.net are advanced enough to offer you that choice.
BUT if you want to create games or embedded software for computers in cars, refrigerators, washing mashines and so on you have to use a language that is not overly bloated due to preinstalled classes. One reason for the need of fast graphic cards is that the pixels are stored in arrays and these arrays must be refreshed the same number of times per second as the framerate of the game.
For a screen resolution of 1280x1024 at a 30 framerate this means updating 39 321 600 arrayed pixels per second (1280x1024x30). So instead of adapting C#, devs just say meh, let's use c++.
Learning a fast language just for things like xrummer would be an overkill as even the slowest blurp will be faster than even the fastest internet connection. The real issue here is taking care of all the specifics of the different forum platforms and their offshoots. The submit button may be titled 'submit', 'post', 'done', 'send' and whatnot and that's just one of many elements that need to be automated. So you need many human work hours to account for all that. If doing it alone takes 100 years, doing it with 10 other people will take 10 years and doing it with 100 people... well you'll be done in one. It's all looping through elements behind the scenes
The real value (imo) in xrummer is that someone has already taken the effort to create a pretty good way to break captchas implementing the latest developments in the field. You can (unoficially) use its engine to solve your own captcha problems. That alone makes it worth its price, again imo.