If your argument is "if they were trying to look good, they'd just make their website better," then I disagree for two reasons:
1) There is a lot more to looking credible then just having a fancy website. The most important thing is that CI's target audience believes that CI provides high-quality care; as Melody explains, Alcor and others are very good at making their services and their staff appear more competent than they actually are.
2) They actually explain why the site looks the way it is on their FAQ page:
[Why don't we] employ a paid professional Webmaster? A website capable of providing information need not be complicated. Fancy presentation also means slow download times, which can be frustrating for some readers.
Fixing their website seems like it would be low-hanging fruit on projecting credibility. It might not be optimally targeted at the sort of credibility they want to optimize for, but it would still be quite efficient.
The FAQ doesn't explain why the site looks the way it does. Their site is difficult to navigate and ugly, and both problems could be solved without making it bulky or complicated. I could design a better website than that, and I'm not even good at designing websites.
I recently found something that may be of concern to some of the readers here.
On her blog, Melody Maxim, former employee of Suspended Animation, provider of "standby services" for Cryonics Institute customers, describes several examples of gross incompetence in providing those services. Specifically, spending large amounts of money on designing and manufacturing novel perfusion equipment when cheaper, more effective devices that could be adapted to serve their purposes already existed, hiring laymen to perform difficult medical procedures who then botched them, and even finding themselves unable to get their equipment loaded onto a plane because it exceeded the weight limit.
An excerpt from one of her posts, "Why I Believe Cryonics Should Be Regulated":