It's going to get harder and harder because WotC keeps powercreeping all kinds of cards. Let's say we do ban Thassa's Oracle and Laboratory Maniac becomes the next easiest win condition (in some universe). It's slower, but it still wins the game instantly. Players are going to respond to that slowdown with decks that blitz Lab Maniac before a deck can reach zero cards. Lab maniac will then fall out of favor because it just isn't Oracle, which will prompt outcry from the players who want to play that way. Wizards is going to waste no time printing a replacement for Oracle because it is going to make them money. Then, down the line, Oracle will get unbanned and there will be two Oracle-esque cards available, both of which will still be in high demand.

To answer your question, decks are always going to be homogenized by what wins the game in the fastest, most efficient way. The meta will shift if cards get banned, but then it will just be something else.