Okay so apparently I'm just doing something wrong and I don't know what the hell to do. Last season I was three wins away from mythic Rank and now all of a sudden I can't even get out of gold four despite the fact that I'm using literally the exact same decks I was using before. Not a single change. Not one. But I can't seem to buy a win. And don't tell me that it's bad luck or RNG because I would believe that if I was just on a bad streak or something but I am using literally the same decks that I was using last season and now all of a sudden I can't win at all. And it's not like I'm at a 50% win rate either. I am getting straight up bodied by decks that are very very very very clearly not gold rank decks.
Has the game logged my progress from last season and decided I need to play against higher ranked players? That's the only plausible explanation I can think of.
I think your entire disposition towards the game seems really hostile and counterproductive right now. Maybe it has to do with making it to diamond so easily last season and you're just expecting the same.
You say you can't get there with the same deck, but you've mostly been posting about random golgari piles and such recently, which doesn't make it seem like you've been grinding with the same old deck. Even with the same deck, you have to remember that the meta changes and, more importantly, improves in deck quality over time.
I don't think "not a gold rank deck" is a thing that exists. People netdeck the top decks in silver, probably even in bronze.
Regarding your last question, you can see your opponent's rank right there in the match. You can start tracking it or you can keep going with the gut feeling of "I know the game is messing with me in some way".