The truth is these days gamblers naturally expect speed and convenience whenever they're gambling so a casino that still struggles with slow withdrawals is already at a disadvantage. Like you rightly said, having a good mix of games is important because not everyone is interested gamble on a particular game. Some people come mainly for slots or table games while others like many of us focus heavily on sports betting. If a casino doesn’t offer what its main audience wants, it’s only natural for players to look elsewhere.
There are casinos which are mainly focused on slot games alone and sports bettors don't have anything to do with them, unless they want to try out something new. It's just these days that it's common to find both slot games and sport in one casino, and even if a casino offers both, what I look at is the type of slot games they have available. I have the regular ones I prefer playing, but trying out something different won't be a bad idea as many of us do try, but the most important thing after the game experience is being able to get off your remaining balance or winnings when you want to without experiencing any form of delay.