I mean I do agree that website doesn't "look" like a website that is a multi-million dollar company website, and it is basically give or take the same design as what it was 10 years ago, with only a few minor changes, I do agree that it needs an overhaul of design changes.
Yes, it's a little strange that they give away so much money in rewards and jackpots but you can't feel that on their website. Their website needs a serious update but probably it's part of their strategy to leave freebitco as it is and as it was years ago to attract nostalgic users. Also, as far as I know, they have other projects (dplay.casino as I am aware) where they build new and innovative gambling platform.
Thinking about the design aspect, even though it's pretty simple and the design is the same since the website was launched more than a decade ago, the website is much superior to many modern crypto platforms which take a long time to load in our devices and don't offer the benefits to users you mentioned like freebitco.in does. I think it's a smart idea to keep the design simple and clean, because besides being nostalgic, it's also accessible to a wider audience, especially the micro earners who don't have access to brand new devices, as they are expensive to be acquired.
Yes, I think also that it's a smart idea (at some point) to keep an old design on website but develop a new platform on brand new casino and promote that one through an old website.
On the contrary, I like the design of freebitco.in. It is not overloaded with effects and animation, there is no bright colour scheme. This is very good and useful for my eyes. It's like freebitco.in is telling you to relax and enjoy gambling. I think freebitco.in doesn't need to review the design changes.