You pick a piece of a much larger problem. Having multiple choices for desktop, apps and distros may or may not be a problem for newbies. But is it really the "main and only" reason behind slow Linux desktop growth? It is not.
Some other people here already mentioned the need of a "killer app". Again, that's not all. There are many different aspects of the problem. Like what OS people get in a store, what OS will they learn on in a school, getting to know that GNU/Linux exists and can be used instead, getting hardware/software to funcion under it, not very good marketing of linux distributions, prejudices, etc.
There are many reasons for low Linux desktop growth. Not a single one. It's nice what you say, unite, remove "useless pieces" and everything will be allright. But it will not. It might be a little bit easier for a newbie in the beginning (not mentioning that almost anyone who develops for GNU/Linux would probably be against), but will that make them stay with GNU/Linux? Hardly. "Being too complex" is a very rare reason for abandoning GNU/Linux, while not being able to run my favorite game or click on the blue E icon to get to internet is much more common.
Linux needs to get its collective act together soon