I got to grandmaster yesterday with a Henselt Machines deck I tuned myself, but still It wasnt a list I completely did myself. I just tweaked the golds and silvers.
So basically, I'm in the top 2000k but that is my limit right now. I understand I'm still uncapable of creating a deck from zero, or using different decks or cards that get my winrate from 60-70% to 80% winrate.
The game is difficult, and you need to check absolutely everything the opponent does, track wich cards he has to play, time the rounds properly, and sometimes take huge gambles. I've managed to shorten many rounds by playing an early Villentrenmeth or make him a decoy so that they need to choose between henselt's target and him, sometimes this prevented me from losing CA, sometimes made me lose the game.
There's also times where I struggle with the timer and end up doing a subotimal play or a not-so-sure play.
Top 2k is like 1% of the player base of gwent, people there are already good, but people in top 100 are either really lucky or different altogeher.
After two months I also noticed stuff like playing only 10 games a day improves my winrate, since I focus much better on the first games than in the games after 3 hours of cotinued play.
I also think if you have a lot of free time, you should be able to climb as long as you are good and lucky. Coin flip is a thing, and if you play enough games you will get a lucky enough streak of 7 games or so and improve your MMR by 100 points or so every now and then.