Lets not kid ourselves. If anything is close to slot machine then it's a classic.
Pulling lever = killing mobs
Hoping 3 icons align = hoping quest items drops
And repeat over again.
Don't even try to use that logic on current wow because LFR player will never be as highly geared as Mythic players. Sure he will get lucky once in a while with titanforge. But it's not even close to RNG you have in classic where you won't see upgrade for months doing dungeons and raids repeatedly.
It's the classic to relies on heavy grind and low droprates that keep you hooked. It's not even cheap tricks, its obvious traps.