OK, let's see:
The Sims, its sequel, and their ludicrous numbers of expansion packs are the textbook definition of ‘mainstream’ in terms of both gameplay, and marketing. And once the brand took hold, it soared. Spore, on the other hand, has no brand power. To gamers it is known, but to the mainstream audience that flocked to The Sims in droves it means nothing.
This is circular reasoning
The Sims didn't became popular because EA made lots of expansions for it.
When they released it, it had virtually no brand brand power, even less than for Spore. Will Wright wasn't even a "Gaming God", and the "Creator Of The Best Selling PC Game Ever" that time, only the "designer of simcity" (in lower-case

).
The Sims didn't mean anything for neither Gamers, nor casuals. But some of the latter tried it, they started talking about it, and buying it. As more people bought it, it became a phenomena, and even more people bought it. As even more people bought it, it became an epic phenomena, and even more people bought it.

In addition, the complexity of the gameplay is going to further ostracise mainstream audiences. There isn’t one simple gameplay mechanic to master in Spore: the game is broken up into seven sections that each play differently to the other.
Regardless of how light the learning curve is, that’s a huge investment to ask of a casual gamer: to learn a multitude of completely different gameplay styles. We know that Maxis’ moto is “everyone should be able to play the game, all the way to the end”, but the question remains, will they bother?
This is just a hardcore game reviewer. It is obvious that his kind is totally unable to rate casual games. Look at any game rating site, they gave terrible ratings for Wii games that are very popular, and fun, just because they didnt understand the point of them.

Maxis is beta testing the game with The Sims audience, trying to make it fun for
them, the real casuals, not for game reviewers who just try thinking like them and fail.

Like hardcore stuff: Diablo for the Creature Phase, Populous for the Tribal Phase, Civilization for the Civilization Phase and Masters of Orion for the Space Phase. Like, c’mon…
*sigh*
These were only rough examples from WW to explain the principles of the stages. Of course the creature stage is not Diablo, not even close to it, it is just also based on getting points and evolving.
I don't think that it is too "hardcore" for anyone to get points and put body parts on a creature.

For proof that online is still a no-go zone for casual gamers just look at the success, or lack thereof, of The Sims Online.
The Sims Online failed because it was multiplayer, not because it was online. A competition based game, for the sandbox audience.
And anyways, it happened in 2002!
Now it is 2008, even little girls can use MSN, MySpace, and Youtube.

The game must launch in an environment saturated with plenty of quality alternatives – from MGS4 to GTA IV, 2008 is the year of software
GTA IV is an alternative for Spore? LOL! That game will be released in a month from now, people will play with it, play more, and forget it by the summer. This is what happens with al thel hardcore games.
And what about ‘multiplayer’. The online aspect of the game is extraordinarily intriguing, but like all online ventures in Australia gamers are prepared for disappointment. For every Halo there is a Prey: a great concept for online mayhem that is buried by our cringe-worthy broadband network.
So... Spore will be a failure just because there is something in it that
could go wrong?
This thinking is like big companies thinking: If there is anything innovative in the game, it might go wrong, so let's do GTA and NFS over and over again!

This guy is much worse than EA, at least
they accepted Spore and it's risk.
It may be playable by all, but it could prove attractive to none.
Says the guy who also said it is: "the most impressive project in development anywhere in the world, on any format. If he pulls it off it truly will be futuristic, mind-blowing stuff." Just like EVERY OTHER PREVIEWER SAID WHO EVER PLAYED THE GAME! They, the hardcore writers ALL agree that this is a great game, but they see to believe that there is a hiding uber-hardcore mass who won't like it.