In principle, someone may even like such a minimalistic style or a retro look. Make it your feature, not a bug
Surely there is an audience of such players who, having looked at such pictures, will become interested and try to play. Maybe he will remember his experience of the game many years ago, when such a design was a normal practice. But besides that, many people may like the primitive design because they don't care how it looks, but they care about how it works. And if it works without problems, then such a casino will suit them. And here, of course, it is important to ensure the good uninterrupted operation of the site.
It is important.
Having a not good user interface (UI) makes the user less attractive to the gambling platform to play with because of course one of the most important to catch the attention of the users is through the visuals that's why UI and UX is important in doing a gambling website by that the next thing is the service of the casino to make sure that the players are keep staying to play with.