Op is looking for a casino that has no lots of games combine, I think the website you've mentioned have variety of games they are offering.
No serious company will want to focus on a single slot game when there are other demands from other games, it is not as if they have this special treatment they offer for players while using a specific game Casino, it is either you win or you lose, most of them will even prefer the loss outcome for players all the time. The last time I checked, most slot games were basically based on pure luck, why would anyone want something that didn't need much skill to win with gambling?
Reputation and trust rate are the things that you must check on a site and not focus on a single game. It's a good thing if a reputable casino site is offering multiple games so you'll have multiple choices of features to enjoy. There will never be a reputable casino site that will only focus on one game.
You didn't include good responsive customer care, a Casino may be good in all areas you have mentioned and still be poor in customer services.