the KYC process shouldn't take long unless the casino is big and there are lots of user requests completing KYC, but it would be a question if a small casino processing KYC takes up to weeks it's confirmed it's fraud because small casinos don't have many active gamblers so there aren't many KYC requests, so obviously it's very weird if they process it slow better leave it or raise the case on this forum if they are active on forums have ANN threads.
In theory, the size of the casino shouldn't have much effect on the KYC processing time. Small ones have fewer customers, but the big one can afford more staff. So what we're really looking at is not the size, but the number of active players per one customer support worker ratio.
But I'd be guessing that nowadays almost all sites that genuinely require KYC (and not just use it as an excuse to not process withdrawals) are using 3rd party verification services rather than handling the process themselves. It's simply cheaper and faster that way and they don't have to deal with all the data protection/storage requirements.