they made an alternative for people to access their site and if it works perfectly when accessed through telegram then their's no big deal or any need to worry since the performance of the site is what matters regardless of where it's being accessed from.
I think some people just want an official game/website/platform to look great. If it looks too cheap, it might imply a lack of budget, a lack of professionalism, a desire to get profit quickly and move on, etc. I can see where they're coming from, although if the platform in question already has a history, then it's more complicated than that (even though backreading a bit suggests the user doesn't mind about it, CMIIW). At the the end of the day a good design will improve the UX anyway.
The players also because of the casino are also different because of the taste or criteria that look at the casino that is in the eyes of this crypto gambling business industry.
So at this point is that you say that you are right, because they may be in agreement or they can agree with the taste they are looking for in the casino and others will be as opposed to it.