Ranking system

Let me say that first of all getting to Diamond is way harder than you think. So congrats on that no joke. I wouldn't call myself a GREAT gamer but I am decent in most online games I play. I solo queued to Diamond last season in Apex my first time.  Any online game I have played in the past seriously so to speak I have been in the top 10% for ranked mode and in a couple cases top 1-2%.  Was Duelist on WoW arenas, GC on Rocket League (played several pros and semis pros and usually got smoked but i would give them a game and once in a blue moon win) . PUBG I solo queued when the game was peaking 7 wins in a row which I know isn't ranked but still there are 98-100 people in the lobby and only 1 of me which I think isn't to shabby. 

Back to my point, Apex is hard. You're playing a game where in ranked you only make up 33% of your team against the best players in the game minus Masters/Preds which are less than 2% of the player base on average.  Also throw in the fact that another ~1% or so of those players are cheating so that also doesn't help. Now take in to account that a good chunk of those teams at Diamond and above are either 2 or 3 people partied up on comms and they play with a strategy. They use their abilities well, they know how to survive, position, and generally are good at shooting. 

Finally if you want to push in Masters level play or high Diamond you need a full team and a lot of time unless you're some freak of talent and even then it probably would still be hard.