Sorry you're having issues with the game! The card pool is two decks shuffled together, so it should be somewhat unlikely to get 7 of the same card, but randomness is randomness and it's always possible. Cards are shuffled back into the combined deck immediately after submitting them, so that can definitely lead to a run of the same value.
I can certainly understand the confusion with Jokers. They can have any card played on them but can't be played on any card (except other jokers). It does make the game easier if you're good at managing your jokers- they tend to be used mostly as the base of new piles, but they also allow some additional freedom to move stacks around you don't get in normal mode. I tried the more intuitive version of the joker but that lead to games that were far too easy.
It doesn't exactly fix the issue you have with getting multiples of a certain suite, but if you would prefer an experience with less RNG I would recommend inverse mode. It's harder than classic in my opinion, but it offers an experience that features a lot more planning ahead.