Woah woah, I had no idea something so little I said a while back ago started this huge debate on whether or not the speculation is silly.
First off, yeah, it is a little demeaning to throw it completely out the window when it actually does have a little backup truth to it. The whole 300 million years thing in the pokedex for both Genesect and Kabutops is enough information to me. You may think its silly, but I don't. No need to get upset over mere speculation.
The Pokedex entrees could very well be the hint from GF you mentioned. They have the same body type, too. It just looks like an extremely modified Kabutops that is so modified that it is basically its own Pokemon and has nothing to do with Kabutops other than it came from it's fossil. Kind of like they took the DNA of Kabutops and "improved" everything that could possibly be altered.
But yeah, please don't debunk a theory that actually has a little evidence. Feel free to rant on the people that would claim they are changing Wailord to a Ghost type or something, however. That's the ridiculous stuff.
Adding on to what I said, I'd like to input that Mew and Mewtwo look almost nothing alike in design. Hardly even the same body type, the only thing I find relatively similar is the tail. I'd bet if Mew and Mewtwo were new Pokemon being released, no one would ever dream of making the connection of Mewtwo being a clone of Mew unless it was stated somewhere like it is now.
Mew and Mewtwo don't have design similarities but have the technical similarities like typing, moves, species, etc. Genesect could very well be the opposite, with similarities in design but nothing in everything else.
That being said, I think it is definitely a fair possibility, but maybe not likely, that Genesect is an altered Kabutops.