Every type of marketing is more or less "gimmicky". Can you tell us what type of marketing/promotion do you consider to be the opposite of "gimmicky"? The bonus/referral programs offered by most casinos are pretty much the only way to attract gamblers nowadays.
The web design of an online casino cannot be improved any further. The online casino games cannot be "upgraded" by adding something new and exciting.
I agree with your point, that most crypto casinos looks pretty much the same, but I don't know how any crypto casino could look different than the successful online fiat casinos.