You are forgetting the most important thing: The gameplay. Sure Jazz looks different. There are none of the old characters. But if you keep an open mind and don't compare it to the other Jazz games, it is a very fun game, although short and easy. Of course, your opinion could be different.

Besides, you should buy it anyway, because we're lucky that we have a new game at all. Opportunities are limited for an old franchise that historically has underachieved in terms of how many people buy it and having a small fan base, regardless of whether or not it is the fault of the companies that were supposed to promote it. If even the dedicated fans show that they are not interested in a new Jazz game, nobody will ever even consider making another game under the Jazz Jackrabbit game.