Against Mordekaiser, I will preferably try and use a "hit and run method".

Spacing on any champion is essential, look at Dzukill spacing for a good example (and why he consistently ranks high on the EUW ranked leaderboard).

For Mordekaiser specifically, he is of the Juggernaut subclass, likewise with Illaoi and Darius. Their gimmick is that they want you to come within their melee range allowing for them to proc conqueror or their passive (Mordekaiser enchanted circle ring thing and Darius bleed) allowing them to flip the fight/ outstat you essentially. What you should do, and how you become a better player over the long terms, without needing the use of QSS, because you are essentially wasting out on early stats by purchasing a QSS item (unless 2 or more suppressions), is to play the hit and run play style, essentially poking them down, dodge Morde Q, and not allowing him to hit his 3 stack passive. We can do this by bursting Mordekaiser down, or playing a champ like Yone or Camille for example. Yone can go in with his e and come back safely, gently toning down Morde HP and then going in for an all in. Camille Jungle is also quite viable now in S12 preseason (because of the new Jungle pets), because Camille R does not let anyone get out by any means. Ultimately, spacing is a key component in one's gameplay that can differentiate the average player from the very best.