Umm... I think what mitchr4 refers as "new" here is from the player side, not the [age of the] site itself, as in the learning curve every people experienced when they're interacting with a platform for the first time.
If you have gambled before then you know what to expect whenever you log in to a similar casino with a different name even if it is a new platform. Almost all casinos offer the same basic features, it is just the arrangements on the platform that is different, and maybe a different name for it.
Only complete noobs without any idea or experience with gambling in an online platform will find it difficult, and slower to understand the platform.
The SportBet.one platform is very user friendly to me, and easy to Navigate.
All casinos virtually have the same games only what makes them different is the name, features and likely bonus they offer to new registered members on their platforms. As you have said, if one is a regular gambler, it would not be too difficult for them to navigate any casino they find themselves in because they are knowledgeable about online casinos and would implore the knowledge they already have in the previous in their current. Newbies are the ones who always complains mostly but however most of their complaints seems to be a noted bug which would latter be discovered and fixed up.
No complaint is a waste of time. Every complaint received is a step to new achievement and development. Once this is done, the casino would find their way to the top as they have envisaged. Every problem solved is a fast way to bigger audience.