It must have both.
Without a reputable name, the casino can't be trusted, and without the good functionality of the website/application, it can't provide players with an enjoyable experience which will eventually lead to the loss of players.
Hopw can you have a reputable name if you're just starting your business?
OP said that many casinos here don't have a good brand name. What does it mean? They aren't trusted? The name of the casino is generic? You have to start somewhere, you can't have reputation right away and I believe most casinos here are reputable, especially those that run signature campaigns for a while.
You can see that a casino is doing well and has money if they can afford to advertise. At the same time a casino that scams will not be allowed to advertise here without serious backlash like negative trust.
Functionality is more important, but I don't see any problems with currently available casino brands